Virtual search area for current picture referencing (cpr) and intra block copy (ibc)

ABSTRACT

Systems and techniques for intra-block copy (IBC) prediction in processing video data include the use of one or more virtual search areas (VSAs) which can be generated to include one or more references to one or more pixels stored in a physical memory. The one or more VSAs can provide references to additional reconstructed sample values that are derived from previously decoded blocks without incurring physical memory use for storage of the additional reconstructed samples. A search area for performing the IBC prediction for a current block of the video data can be extended to include the one or more VSAs. Extending the search area to include the one or more VSAs provides the IBC prediction with additional search area for finding one or more prediction blocks or prediction samples without having to utilize physical memory to store the additional reconstructed samples from previously decoded blocks.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/783,180, filed on Dec. 20, 2018, which is hereby incorporated byreference, in its entirety and for all purposes.

FIELD

The present disclosure generally relates to video coding andcompression, and more specifically to techniques and systems relating toIntra-Block Copy (IBC) or Current Picture Referencing (CPR).

BACKGROUND

Many devices and systems allow video data to be processed and output forconsumption. Digital video data includes large amounts of data to meetthe demands of consumers and video providers. For example, consumers ofvideo data desire video of the utmost quality, with high fidelity,resolutions, frame rates, and the like. As a result, the large amount ofvideo data that is required to meet these demands places a burden oncommunication networks and devices that process and store the videodata.

Various video coding techniques may be used to compress video data.Video coding is performed according to one or more video codingstandards. For example, video coding standards include high-efficiencyvideo coding (HEVC), advanced video coding (AVC), MPEG-2 Part 2 coding(MPEG stands for moving picture experts group), VP9, Alliance of OpenMedia (AOMedia) Video 1 (AV1), Essential Video Coding (EVC), or thelike. Video coding generally utilizes prediction methods (e.g.,inter-prediction, intra-prediction, or the like) that take advantage ofredundancy present in video images or sequences. An important goal ofvideo coding techniques is to compress video data into a form that usesa lower bit rate, while avoiding or minimizing degradations to videoquality. With ever-evolving video services becoming available, encodingtechniques with better coding efficiency are needed.

BRIEF SUMMARY

Intra-block copy (IBC) (also referred to as Current Picture Referencing(CPR)) is an intra-prediction technique for predicting a block of apicture of video data from one or more reconstructed pixels ofpreviously decoded blocks of the picture. In some cases, the previouslydecoded blocks used by IBC can include unfiltered previously decodedblocks (e.g., before in-loop filtering). Using redundancy in an imagepicture or frame. IBC performs block matching to predict a block ofsamples as a displacement from a reconstructed block of samples in aneighboring or a non-neighboring region of the picture. By removing theredundancy from repeating patterns of content, the IBC prediction canimprove coding efficiency, but can consume additional storage space forstoring reconstructed pixels (e.g., unfiltered reconstructed pixels).

One or more systems and methods of coding are described herein forenhancing the search area for IBC prediction. In some cases, the systemsand methods described herein can address the storage space utilizationfor the IBC prediction. In some examples, the number of samples madeavailable for IBC prediction can be increased without incurringadditional storage space. In some examples, one or more virtual searchareas (VSAs) can be generated to include one or more references to oneor more pixels stored in a physical memory. In some cases, the one ormore references to the one or more pixels stored in the physical memorycan effectively constitute pixel padding without incurring pixel storagespace in the physical memory for the padded pixels. The search area forperforming the IBC prediction for a current block can be extended toinclude the virtual search area (e.g., the padding pixels of the virtualsearch area). For example, the virtual search area can provide areference to additional reconstructed sample values that are derivedfrom previously decoded blocks without incurring physical memory use forstorage of the additional reconstructed samples. In some examples,extending the search area to include the virtual search area providesthe IBC prediction being performed for the current block with additionalsearch area (i.e., search area being virtual in that pixel values withinthe search area are not stored in physical memory) for finding aprediction block or prediction samples without having to utilizephysical memory to store the additional reconstructed samples frompreviously decoded blocks referenced above.

According to at least one example, a method of decoding video data isprovided. The method includes obtaining an encoded video bitstreamincluding video data. The method further includes generating a virtualsearch area for performing intra-block copy prediction for a currentblock of the video data, the virtual search area including one or morereferences to one or more pixels stored in a physical memory. The methodfurther includes extending a search area for performing the intra-blockcopy prediction for the current block to include the virtual searcharea.

In another example, an apparatus for decoding video data is provided.The apparatus includes a memory and a processor implemented incircuitry. The processor is configured to and can obtain an encodedvideo bitstream including video data. The processor is furtherconfigured to and can generate a virtual search area for performingintra-block copy prediction for a current block of the video data, thevirtual search area including one or more references to one or morepixels stored in a physical memory. The processor is further configuredto and can extend a search area for performing the intra-block copyprediction for the current block to include the virtual search area.

In another example, a non-transitory computer-readable medium isprovided that has stored thereon instructions that, when executed by oneor more processors, cause the one or more processors to: obtain anencoded video bitstream including video data; generate a virtual searcharea for performing intra-block copy prediction for a current block ofthe video data, the virtual search area including one or more referencesto one or more pixels stored in a physical memory; and extend a searcharea for performing the intra-block copy prediction for the currentblock to include the virtual search area.

In another example, an apparatus for decoding video data is provided.The apparatus includes means for obtaining an encoded video bitstreamincluding video data. The apparatus further includes means forgenerating a virtual search area for performing intra-block copyprediction for a current block of the video data, the virtual searcharea including one or more references to one or more pixels stored in aphysical memory. The apparatus further includes means for extending asearch area for performing the intra-block copy prediction for thecurrent block to include the virtual search area.

According to at least one example, a method of encoding video data isprovided. The method includes obtaining a current block of a picture ofvideo data. The method further includes generating a virtual search areafor performing intra-block copy prediction for the current block, thevirtual search area including one or more references to one or morepixels stored in a physical memory. The method further includesextending a search area for performing the intra-block copy predictionfor the current block to include the virtual search area. The methodfurther includes generating an encoded video bitstream including atleast a portion of the current block.

In another example, an apparatus for encoding video data is provided.The apparatus includes a memory and a processor implemented incircuitry. The processor is configured to and can obtain a current blockof a picture of video data. The processor is further configured to andcan generate a virtual search area for performing intra-block copyprediction for a current block of the video data, the virtual searcharea including one or more references to one or more pixels stored in aphysical memory. The processor is further configured to and can extend asearch area for performing the intra-block copy prediction for thecurrent block to include the virtual search area.

In another example, a non-transitory computer-readable medium isprovided that has stored thereon instructions that, when executed by oneor more processors, cause the one or more processors to: obtain anencoded video bitstream including video data; generate a virtual searcharea for performing intra-block copy prediction for a current block ofthe video data, the virtual search area including one or more referencesto one or more pixels stored in a physical memory; extend a search areafor performing the intra-block copy prediction for the current block toinclude the virtual search area; and generate an encoded video bitstreamincluding at least a portion of the current block.

In another example, an apparatus for encoding video data is provided.The apparatus includes means for obtaining a current block of a pictureof video data. The apparatus further includes means for generating avirtual search area for performing intra-block copy prediction for acurrent block of the video data, the virtual search area including oneor more references to one or more pixels stored in a physical memory.The apparatus further includes means for extending a search area forperforming the intra-block copy prediction for the current block toinclude the virtual search area. The apparatus further includes meansfor generating an encoded video bitstream including at least a portionof the current block.

In some aspects of the methods, apparatuses, and computer-readable mediadescribed above, the physical memory includes a circular buffer forstoring reconstructed pixels of a coding unit comprising one or moreblocks of the video data.

In some aspects of the methods, apparatuses, and computer-readable mediadescribed above, the one or more pixels stored in the physical memoryinclude reconstructed pixels belonging to a boundary of the coding unit.

In some aspects of the methods, apparatuses, and computer-readable mediadescribed above, the one or more references to the one or more pixelsstored in the physical memory include repeated references to thereconstructed pixels belonging to the boundary.

In some aspects of the methods, apparatuses, and computer-readable mediadescribed above, the repeated references to the reconstructed pixelsbelonging to the boundary include a first reference to at least onereconstructed pixel belonging to the boundary and a second reference tothe at least one reconstructed pixel belonging to the boundary.

In some aspects of the methods, apparatuses, and computer-readable mediadescribed above, the current block belongs to the coding unit.

In some aspects of the methods, apparatuses, and computer-readable mediadescribed above, the coding unit includes two or more virtual pipelinedata units (VPDUs), at least one VPDU of the two or more VPDUs includingthe current block, and wherein at least a portion of the circular bufferis configured to store reconstructed pixels of the at least one VPDUwhile intra-block copy prediction is being performed on the one or moreblocks of the at least one VPDU.

In some aspects of the methods, apparatuses, and computer-readable mediadescribed above, at least the portion of the circular buffer isunavailable for storing pixels of the search area for performing theintra-block copy prediction for the current block.

In some aspects of the methods, apparatuses, and computer-readable mediadescribed above, the physical memory comprises a line buffer for storingreconstructed pixels of one or more blocks of the video data.

In some aspects of the methods, apparatuses, and computer-readable mediadescribed above, the one or more blocks belong to a neighboring codingunit of a current coding unit comprising the current block.

In some aspects of the methods, apparatuses, and computer-readable mediadescribed above, the one or more references to the one or more pixelsstored in the physical memory include repeated references to thereconstructed pixels stored in the line buffer.

In some aspects of the methods, apparatuses, and computer-readable mediadescribed above, the repeated references to the reconstructed pixelsstored in the line buffer comprise a first reference to at least onereconstructed pixel stored in the line buffer and a second reference tothe at least one reconstructed pixel stored in the line buffer.

Some aspects of the methods, apparatuses, and computer-readable mediadescribed above further include performing the intra-block copyprediction for the current block using one or more references to one ormore pixels in the virtual search area.

Some aspects of the methods, apparatuses, and computer-readable mediadescribed above further include reconstructing the current block basedon a prediction value obtained using the intra-block copy prediction anda residual value.

This summary is not intended to identify key or essential features ofthe claimed subject matter, nor is it intended to be used in isolationto determine the scope of the claimed subject matter. The subject mattershould be understood by reference to appropriate portions of the entirespecification of this patent, any or all drawings, and each claim.

The foregoing, together with other features and embodiments, will becomemore apparent upon referring to the following specification, claims, andaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative embodiments of the present application are described indetail below with reference to the following drawing:

FIG. 1 is a block diagram illustrating an example of an encoding deviceand a decoding device, in accordance with some examples;

FIG. 2 is a block diagram illustrating an example of a coded picture forwhich an intra-block copy prediction mode is applied, in accordance withsome examples;

FIG. 3 is a block diagram illustrating another example of intra-blockcopy prediction mode, in accordance with some examples;

FIG. 4 is a diagram illustrating an example of a 128×128 coding treeunit (CTU) that is split into 64×64 blocks in pipeline processing, inaccordance with some examples;

FIG. 5 is a diagram illustrating an example of a current CTU's virtualsearch area, in accordance with some examples;

FIG. 6 is a diagram illustrating an example of a virtual search areawith a makeup area, in accordance with some examples;

FIG. 7A is a diagram illustrating an example of a virtual search areafor a shared storage case, in accordance with some examples;

FIG. 7B is a diagram illustrating another example of a virtual searcharea for a shared storage case, in accordance with some examples;

FIG. 8 is a flowchart illustrating an example of a process of encodingvideo data including performing intra-block copy prediction using avirtual search area, in accordance with some examples;

FIG. 9 is a flowchart illustrating an example of a process of decodingvideo data including performing intra-block copy prediction using avirtual search area, in accordance with some examples;

FIG. 10 is a block diagram illustrating an example video encodingdevice, in accordance with some embodiments.

FIG. 11 is a block diagram illustrating an example video decodingdevice, in accordance with some embodiments.

DETAILED DESCRIPTION

Certain aspects and embodiments of this disclosure are provided below.Some of these aspects and embodiments may be applied independently andsome of them may be applied in combination as would be apparent to thoseof skill in the art. In the following description, for the purposes ofexplanation, specific details are set forth in order to provide athorough understanding of embodiments of the application. However, itwill be apparent that various embodiments may be practiced without thesespecific details. The figures and description are not intended to berestrictive.

The ensuing description provides exemplary embodiments only, and is notintended to limit the scope, applicability, or configuration of thedisclosure. Rather, the ensuing description of the exemplary embodimentswill provide those skilled in the art with an enabling description forimplementing an exemplary embodiment. It should be understood thatvarious changes may be made in the function and arrangement of elementswithout departing from the spirit and scope of the application as setforth in the appended claims.

Video coding devices implement video compression techniques to encodeand decode video data efficiently. Video compression techniques mayinclude applying different prediction modes, including spatialprediction (e.g., intra-frame prediction or intra-prediction), temporalprediction (e.g., inter-frame prediction or inter-prediction),inter-layer prediction (across different layers of video data, and/orother prediction techniques to reduce or remove redundancy inherent invideo sequences. A video encoder can partition each picture of anoriginal video sequence into rectangular regions referred to as videoblocks or coding units (described in greater detail below). These videoblocks may be encoded using a particular prediction mode.

Video blocks may be divided in one or more ways into one or more groupsof smaller blocks. Blocks can include coding tree blocks, predictionblocks, transform blocks, or other suitable blocks. References generallyto a “block,” unless otherwise specified, may refer to such video blocks(e.g., coding tree blocks, coding blocks, prediction blocks, transformblocks, or other appropriate blocks or sub-blocks, as would beunderstood by one of ordinary skill. Further, each of these blocks mayalso interchangeably be referred to herein as “units” (e.g., coding treeunit (CTU), coding unit, prediction unit (PU), transform unit (TU), orthe like). In some cases, a unit may indicate a coding logical unit thatis encoded in a bitstream, while a block may indicate a portion of videoframe buffer a process is target to.

For inter-prediction modes, a video encoder can search for a blocksimilar to the block being encoded in a frame (or picture) located inanother temporal location, referred to as a reference frame or areference picture. The video encoder may restrict the search to acertain spatial displacement from the block to be encoded. A best matchmay be located using a two-dimensional (2D) motion vector that includesa horizontal displacement component and a vertical displacementcomponent. For intra-prediction modes, a video encoder may form thepredicted block using spatial prediction techniques based on data frompreviously encoded neighboring blocks within the same picture.

The video encoder may determine a prediction error. For example, theprediction can be determined as the difference between the pixel valuesin the block being encoded and the predicted block. The prediction errorcan also be referred to as the residual. The video encoder may alsoapply a transform to the prediction error (e.g., a discrete cosinetransform (DCT) or other suitable transform) to generate transformcoefficients. After transformation, the video encoder may quantize thetransform coefficients. The quantized transform coefficients and motionvectors may be represented using syntax elements, and, along withcontrol information, form a coded representation of a video sequence. Insome instances, the video encoder may entropy code syntax elements,thereby further reducing the number of bits needed for theirrepresentation.

A video decoder may, using the syntax elements and control informationdiscussed above, construct predictive data (e.g., a predictive block)for decoding a current frame. For example, the video decoder may add thepredicted block and the compressed prediction error. The video decodermay determine the compressed prediction error by weighting the transformbasis functions using the quantized coefficients. The difference betweenthe reconstructed frame and the original frame is called reconstructionerror.

Several systems and methods of video coding using video encoders,decoders, and other coding processing devices are described herein. Insome examples, one or more systems and methods of video coding aredescribed for performing Intra-Block Copy (IBC) or Current PictureReferencing (CPR). For example, the one or more systems and methodsdescribed herein provide performance improvements and complexityreduction of IBC and CPR. The techniques described herein can be appliedto any of the existing video codecs, such as High Efficiency VideoCoding (HEVC), Versatile Video Coding (VVC), Advanced Video Coding(AVC), or the like, and/or can be an efficient coding tool in any futurevideo coding standards. In some cases, the systems and methods describedherein can be used for screen content coding, including the support ofpossibly high bit depth (more than 8 bits), different chroma samplingformats (e.g., such as 4:4:4, 4:2:2, 4:2:0, 4:0:0, among others). Thesystems and methods can also be applied to coding of other video and/orstill image content.

FIG. 1 is a block diagram illustrating an example of a system 100including an encoding device 104 and a decoding device 112. The encodingdevice 104 may be part of a source device, and the decoding device 112may be part of a receiving device. The source device and/or thereceiving device may include an electronic device, such as a mobile orstationary telephone handset (e.g., smartphone, cellular telephone, orthe like), a desktop computer, a laptop or notexbook computer, a tabletcomputer, a set-top box, a television, a camera, a display device, adigital media player, a video gaming console, a video streaming device,an Internet Protocol (IP) camera, or any other suitable electronicdevice. In some examples, the source device and the receiving device mayinclude one or more wireless transceivers for wireless communications.The coding techniques described herein are applicable to video coding invarious multimedia applications, including streaming video transmissions(e.g., over the Internet), television broadcasts or transmissions,encoding of digital video for storage on a data storage medium, decodingof digital video stored on a data storage medium, or other applications.In some examples, system 100 can support one-way or two-way videotransmission to support applications such as video conferencing, videostreaming, video playback, video broadcasting, gaming, and/or videotelephony.

The encoding device 104 (or encoder) can be used to encode video datausing a video coding standard or protocol to generate an encoded videobitstream. Examples of video coding standards include ITU-T H.261,ISO/IEC MPEG-1 Visual, ITU-T H1.262 or ISO/IEC MPEG-2 Visual, ITU-TH.263, ISO/IEC MPEG-4 Visual, ITU-T H.264 (also known as ISO/IEC MPEG-4AVC), including its Scalable Video Coding (SVC) and Multiview VideoCoding (MVC) extensions, and High Efficiency Video Coding (HEVC) orITU-T H.265. Various extensions to HEVC deal with multi-layer videocoding exist, including the range and screen content coding extensions,3D video coding (3D-HEVC) and multiview extensions (MV-HEVC) andscalable extension (SHVC). The HEVC and its extensions have beendeveloped by the Joint Collaboration Team on Video Coding (JCT-VC) aswell as Joint Collaboration Team on 3D Video Coding ExtensionDevelopment (JCT-3V) of ITU-T Video Coding Experts Group (VCEG) andISO/IEC Motion Picture Experts Group (MPEG).

MPEG and ITU-T VCEG have also formed a joint exploration video team(JVET) to explore new coding tools for the next generation of videocoding standard, named Versatile Video Coding (VVC). The referencesoftware is called VVC Test Model (VTM). An objective of VVC is toprovide a significant improvement in compression performance over theexisting HEVC standard, aiding in deployment of higher-quality videoservices and emerging applications (e.g., such as 360° omnidirectionalimmersive multimedia, high-dynamic-range (HDR) video, among others).VP9, Alliance of Open Media (AOMedia) Video 1 (AV1), and Essential VideoCoding (EVC) are other video coding standards for which the techniquesdescribed herein can be applied.

Many embodiments described herein can be performed using video codecssuch as VTM, VVC, HEVC, AVC, and/or extensions thereof. However, thetechniques and systems described herein may also be applicable to othercoding standards, such as MPEG, JPEG (or other coding standard for stillimages), VP9, AV1, extensions thereof, or other suitable codingstandards already available or not yet available or developed.Accordingly, while the techniques and systems described herein may bedescribed with reference to a particular video coding standard, one ofordinary skill in the art will appreciate that the description shouldnot be interpreted to apply only to that particular standard.

Referring to FIG. 1, a video source 102 may provide the video data tothe encoding device 104. The video source 102 may be part of the sourcedevice, or may be part of a device other than the source device. Thevideo source 102 may include a video capture device (e.g., a videocamera, a camera phone, a video phone, or the like), a video archivecontaining stored video, a video server or content provider providingvideo data, a video feed interface receiving video from a video serveror content provider, a computer graphics system for generating computergraphics video data, a combination of such sources, or any othersuitable video source.

The video data from the video source 102 may include one or more inputpictures or frames. A picture or frame is a still image that, in somecases, is part of a video. In some examples, data from the video source102 can be a still image that is not a part of a video. In HEVC, VVC,and other video coding specifications, a video sequence can include aseries of pictures. A picture may include three sample arrays, denotedS_(L), S_(Cb), and S_(Cr). S_(L) is a two-dimensional array of lumasamples, S_(Cb) is a two-dimensional array of Cb chrominance samples,and S_(Cr) is a two-dimensional array of Cr chrominance samples.Chrominance samples may also be referred to herein as “chroma” samples.In other instances, a picture may be monochrome and may only include anarray of luma samples.

The encoder engine 106 (or encoder) of the encoding device 104 encodesthe video data to generate an encoded video bitstream. In some examples,an encoded video bitstream (or “video bitstream” or “bitstream”) is aseries of one or more coded video sequences. A coded video sequence(CVS) includes a series of access units (AUs) starting with an AU thathas a random access point picture in the base layer and with certainproperties up to and not including a next AU that has a random accesspoint picture in the base layer and with certain properties. Forexample, the certain properties of a random access point picture thatstarts a CVS may include a RASL flag (e.g., NoRaslOutputFlag) equalto 1. Otherwise, a random access point picture (with RASL flag equal to0) does not start a CVS. An access unit (AU) includes one or more codedpictures and control information corresponding to the coded picturesthat share the same output time. Coded slices of pictures areencapsulated in the bitstream level into data units called networkabstraction layer (NAL) units. For example, an HEVC video bitstream mayinclude one or more CVSs including NAL units. Each of the NAL units hasa NAL unit header. In one example, the header is one-byte for H.264/AVC(except for multi-layer extensions) and two-byte for HEVC. The syntaxelements in the NAL unit header take the designated bits and thereforeare visible to all kinds of systems and transport layers, such asTransport Stream, Real-time Transport (RTP) Protocol, File Format, amongothers.

Two classes of NAL units exist in the HEVC standard, including videocoding layer (VCL) NAL units and non-VCL NAL units. A VCL NAL unitincludes one slice or slice segment (described below) of coded picturedata, and a non-VCL NA L unit includes control information that relatesto one or more coded pictures. In some cases, a NAL unit can be referredto as a packet. An HEVC AU includes VCL NAL units containing codedpicture data and non-VCL NAL units (if any) corresponding to the codedpicture data.

NAL units may contain a sequence of bits forming a coded representationof the video data (e.g., an encoded video bitstream, a CVS of abitstream, or the like), such as coded representations of pictures in avideo. The encoder engine 106 generates coded representations ofpictures by partitioning each picture into multiple slices. A slice isindependent of other slices so that information in the slice is codedwithout dependency on data from other slices within the same picture. Aslice includes one or more slice segments including an independent slicesegment and, if present, one or more dependent slice segments thatdepend on previous slice segments.

In HEVC, the slices are then partitioned into coding tree blocks (CTBs)of luma samples and chroma samples. A CTB of luma samples and one ormore CTBs of chroma samples, along with syntax for the samples, arereferred to as a coding tree unit (CTU). A CTU may also be referred toas a “tree block” or a “largest coding unit” (LCU). A CTU is the basicprocessing unit for HEVC encoding. A CTU can be split into multiplecoding units (CUs) of varying sizes. A CU contains luma and chromasample arrays that are referred to as coding blocks (CBs).

The luma and chroma CBs can be further split into prediction blocks(PBs). A PB is a block of samples of the luma component or a chromacomponent that uses the same motion parameters for inter-prediction orintra-block copy (IBC) prediction (when available or enabled for use).The luma PB and one or more chroma PBs, together with associated syntax,form a prediction unit (PU). For inter-prediction, a set of motionparameters (e.g., one or more motion vectors, reference indices, or thelike) is signaled in the bitstream for each PU and is used forinter-prediction of the luma PB and the one or more chroma PBs. Themotion parameters can also be referred to as motion information. A CBcan also be partitioned into one or more transform blocks (TBs). A TBrepresents a square block of samples of a color component on which aresidual transform (e.g., the same two-dimensional transform in somecases) is applied for coding a prediction residual signal. A transformunit (TU) represents the TBs of luma and chroma samples, andcorresponding syntax elements. Transform coding is described in moredetail below.

A size of a CU corresponds to a size of the coding mode and may besquare in shape. For example, a size of a CU may be 8×8 samples, 16×16samples, 32×32 samples, 64×64 samples, or any other appropriate size upto the size of the corresponding CTU. The phrase “N×N” is used herein torefer to pixel dimensions of a video block in terms of vertical andhorizontal dimensions (e.g., 8 pixels×8 pixels). The pixels in a blockmay be arranged in rows and columns. In some embodiments, blocks may nothave the same number of pixels in a horizontal direction as in avertical direction. Syntax data associated with a CU may describe, forexample, partitioning of the CU into one or more PUs. Partitioning modesmay differ between whether the CU is intra-prediction mode encoded orinter-prediction mode encoded. PUs may be partitioned to be non-squarein shape. Syntax data associated with a CU may also describe, forexample, partitioning of the CU into one or more TUs according to a CTU.A TU can be square or non-square in shape.

According to the H EVC standard, transformations may be performed usingtransform units (TUs). TUs may vary for different CUs. The TUs may besized based on the size of PUs within a given CU. The TUs may be thesame size or smaller than the PUs. In some examples, residual samplescorresponding to a CU may be subdivided into smaller units using aquadtree structure known as residual quad tree (RQT). Leaf nodes of theRQT may correspond to TUs. Pixel difference values associated with theTUs may be transformed to produce transform coefficients. The transformcoefficients may then be quantized by the encoder engine 106.

Once the pictures of the video data are partitioned into CUs, theencoder engine 106 predicts each PU using a prediction mode. Theprediction unit or prediction block is then subtracted from the originalvideo data to get residuals (described below). For each CU, a predictionmode may be signaled inside the bitstream using syntax data. Aprediction mode may include intra-prediction (or intra-pictureprediction) or inter-prediction (or inter-picture prediction).Intra-prediction utilizes the correlation between spatially neighboringsamples within a picture. For example, using intra-prediction, each PUis predicted from neighboring image data in the same picture using, forexample, DC prediction to find an average value for the PU, planarprediction to fit a planar surface to the PU, direction prediction toextrapolate from neighboring data, or any other suitable types ofprediction. Inter-prediction uses the temporal correlation betweenpictures in order to derive a motion-compensated prediction for a blockof image samples. For example, using inter-prediction, each PU ispredicted using motion compensation prediction from image data in one ormore reference pictures (before or after the current picture in outputorder). The decision whether to code a picture area using inter-pictureor intra-picture prediction may be made, for example, at the CU level.

The encoder engine 106 and decoder engine 116 (described in more detailbelow) may be configured to operate according to VVC. According to VVC,a video coder (such as encoder engine 106 and/or decoder engine 116)partitions a picture into a plurality of coding tree units (CTUs) (wherea CTB of luma samples and one or more CTBs of chroma samples, along withsyntax for the samples, are referred to as a CTU). The video coder canpartition a CTU according to a tree structure, such as a quadtree-binarytree (QTBT) structure or Multi-Type Tree (MTT) structure. The QTBTstructure removes the concepts of multiple partition types, such as theseparation between CUs, PUs, and TUs of HEVC. A QTBT structure includestwo levels, including a first level partitioned according to quadtreepartitioning, and a second level partitioned according to binary treepartitioning. A root node of the QTBT structure corresponds to a CTU.Leaf nodes of the binary trees correspond to coding units (CUs).

In an MTT partitioning structure, blocks may be partitioned using aquadtree partition, a binary tree partition, and one or more types oftriple tree partitions. A triple tree partition is a partition where ablock is split into three sub-blocks. In some examples, a triple treepartition divides a block into three sub-blocks without dividing theoriginal block through the center. The partitioning types in MTT (e.g.,quadtree, binary tree, and tripe tree) may be symmetrical orasymmetrical.

In some examples, the video coder can use a single QTBT or MTT structureto represent each of the luminance and chrominance components, while inother examples, the video coder can use two or more QTBT or MTTstructures, such as one QTBT or MTT structure for the luminancecomponent and another QTBT or MTT structure for both chrominancecomponents (or two QTBT and/or MTT structures for respective chrominancecomponents).

The video coder can be configured to use quadtree partitioning per HEVC,QTBT partitioning, MTT partitioning, or other partitioning structures.For illustrative purposes, the description herein may refer to QTBTpartitioning. However, it should be understood that the techniques ofthis disclosure may also be applied to video coders configured to usequadtree partitioning, or other types of partitioning as well.

In some examples, the one or more slices of a picture are assigned aslice type. Slice types include an I slice, a P slice, and a B slice. AnI slice (intra-frames, independently decodable) is a slice of a picturethat is only coded by intra-prediction, and therefore is independentlydecodable since the I slice requires only the data within the frame topredict any prediction unit or prediction block of the slice. A P slice(uni-directional predicted frames) is a slice of a picture that may becoded with intra-prediction and with uni-directional inter-prediction.Each prediction unit or prediction block within a P slice is eithercoded with Intra prediction or inter-prediction. When theinter-prediction applies, the prediction unit or prediction block isonly predicted by one reference picture, and therefore reference samplesare only from one reference region of one frame. A B slice(hi-directional predictive frames) is a slice of a picture that may becoded with intra-prediction and with inter-prediction (e.g., eitherbi-prediction or uni-prediction). A prediction unit or prediction blockof a B slice may be bi-directionally predicted from two referencepictures, where each picture contributes one reference region and samplesets of the two reference regions are weighted (e.g., with equal weightsor with different weights) to produce the prediction signal of thebi-directional predicted block. As explained above, slices of onepicture are independently coded. In some cases, a picture can be codedas just one slice.

As noted above, intra-picture prediction utilizes the correlationbetween spatially neighboring samples within a picture. There are aplurality of intra-prediction modes (also referred to as “intra modes”).In some examples, the intra prediction of a luma block includes 35modes, including the Planar mode, DC mode, and 33 angular modes (e.g.,diagonal intra prediction modes and angular modes adjacent to thediagonal intra prediction modes). The 35 modes of the intra predictionare indexed as shown in Table 1 below. In other examples, more intramodes may be defined including prediction angles that may not already berepresented by the 33 angular modes. In other examples, the predictionangles associated with the angular modes may be different from thoseused in HEVC.

TABLE 1 Specification of intra prediction mode and associated namesIntra- prediction mode Associated name 0 INTRA_PLANAR 1 INTRA_DC 2 . . .34 INTRA_ANGULAR2 . . . INTRA_ANGULAR34

Inter-picture prediction uses the temporal correlation between picturesin order to derive a motion-compensated prediction for a block of imagesamples. Using a translational motion model, the position of a block ina previously decoded picture (a reference picture) is indicated by amotion vector (Δx, Δy), with Δx specifying the horizontal displacementand Δy specifying the vertical displacement of the reference blockrelative to the position of the current block. In some cases, a motionvector (Δx, Δy) can be in integer sample accuracy (also referred to asinteger accuracy), in which case the motion vector points to theinteger-pel grid (or integer-pixel sampling grid) of the referenceframe. In some cases, a motion vector (Δx, Δy) can be of fractionalsample accuracy (also referred to as fractional-pel accuracy ornon-integer accuracy) to more accurately capture the movement of theunderlying object, without being restricted to the integer-pel grid ofthe reference frame. Accuracy of motion vectors may be expressed by thequantization level of the motion vectors. For example, the quantizationlevel may be integer accuracy (e.g., 1-pixel) or fractional-pel accuracy(e.g., ¼-pixel, ½-pixel, or other sub-pixel value). Interpolation isapplied on reference pictures to derive the prediction signal when thecorresponding motion vector has fractional sample accuracy. For example,samples available at integer positions can be filtered (e.g., using oneor more interpolation filters) to estimate values at fractionalpositions. The previously decoded reference picture is indicated by areference index (refIdx) to a reference picture list. The motion vectorsand reference indices can be referred to as motion parameters. Two kindsof inter-picture prediction can be performed, including uni-predictionand bi-prediction.

With inter-prediction using bi-prediction, two sets of motion parameters(Δx₀, y₀, refIdx₀ and Δx₁, y₁, refIdx₁) are used to generate two motioncompensated predictions (from the same reference picture or possiblyfrom different reference pictures). For example, with bi-prediction,each prediction block uses two motion compensated prediction signals,and generates B prediction units. The two motion compensated predictionsare then combined to get the final motion compensated prediction. Forexample, the two motion compensated predictions can be combined byaveraging. In another example, weighted prediction can be used, in whichcase different weights can be applied to each motion compensatedprediction. The reference pictures that can be used in bi-prediction arestored in two separate lists, denoted as list 0 and list 1. Motionparameters can be derived at the encoder using a motion estimationprocess.

With inter-prediction using uni-prediction, one set of motion parameters(Δx₀, y₀, refIdx₀) is used to generate a motion compensated predictionfrom a reference picture. For example, with uni-prediction, eachprediction block uses at most one motion compensated prediction signal,and generates P prediction units.

A PU may include the data (e.g., motion parameters or other suitabledata) related to the prediction process. For example, when the PU isencoded using intra-prediction, the PU may include data describing anintra-prediction mode for the PU. As another example, when the PU isencoded using inter-prediction, the PU may include data defining amotion vector for the PU. The data defining the motion vector for a PUmay describe, for example, a horizontal component of the motion vector(Δx), a vertical component of the motion vector (Δy), a resolution forthe motion vector (e.g., integer precision, one-quarter pixel precisionor one-eighth pixel precision), a reference picture to which the motionvector points, a reference index, a reference picture list (e.g., List0, List 1, or List C) for the motion vector, or any combination thereof.

After performing prediction using intra- and/or inter-prediction, theencoding device 104 can perform transformation and quantization. Forexample, following prediction, the encoder engine 106 may calculateresidual values corresponding to the PU. Residual values may comprisepixel difference values between the current block of pixels being coded(the PU) and the prediction block used to predict the current block(e.g., the predicted version of the current block). For example, aftergenerating a prediction block (e.g., issuing inter-prediction orintra-prediction), the encoder engine 106 can generate a residual blockby subtracting the prediction block produced by a prediction unit fromthe current block. The residual block includes a set of pixel differencevalues that quantify differences between pixel values of the currentblock and pixel values of the prediction block. In some examples, theresidual block may be represented in a two-dimensional block format(e.g., a two-dimensional matrix or array of pixel values). In suchexamples, the residual block is a two-dimensional representation of thepixel values.

Any residual data that may be remaining after prediction is performed istransformed using a block transform, which may be based on discretecosine transform, discrete sine transform, an integer transform, awavelet transform, other suitable transform function, or any combinationthereof. In some cases, one or more block transforms (e.g., sizes 32×32,16×16, 8×8, 4×4, or other suitable size) may be applied to residual datain each CU. In some embodiments, a TU may be used for the transform andquantization processes implemented by the encoder engine 106. A given CUhaving one or more PUs may also include one or more TUs. As described infurther detail below, the residual values may be transformed intotransform coefficients using the block transforms, and then may bequantized and scanned using TUs to produce serialized transformcoefficients for entropy coding.

In some embodiments following intra-predictive or inter-predictivecoding using PUs of a CU, the encoder engine 106 may calculate residualdata for the TUs of the CU. The PUs may comprise pixel data in thespatial domain (or pixel domain). The TUs may comprise coefficients inthe transform domain following application of a block transform. Aspreviously noted, the residual data may correspond to pixel differencevalues between pixels of the unencoded picture and prediction valuescorresponding to the PUs. Encoder engine 106 may form the TUs includingthe residual data for the CU, and may then transform the TUs to producetransform coefficients for the CU.

The encoder engine 106 may perform quantization of the transformcoefficients. Quantization provides further compression by quantizingthe transform coefficients to reduce the amount of data used torepresent the coefficients. For example, quantization may reduce the bitdepth associated with some or all of the coefficients. In one example, acoefficient with an n-bit value may be rounded down to an m-bit valueduring quantization, with n being greater than m.

Once quantization is performed, the coded video bitstream includesquantized transform coefficients, prediction information (e.g.,prediction modes, motion vectors, block vectors, or the like),partitioning information, and any other suitable data, such as othersyntax data. The different elements of the coded video bitstream maythen be entropy encoded by the encoder engine 106. In some examples, theencoder engine 106 may utilize a predefined scan order to scan thequantized transform coefficients to produce a serialized vector that canbe entropy encoded. In some examples, encoder engine 106 may perform anadaptive scan. After scanning the quantized transform coefficients toform a vector (e.g., a one-dimensional vector), the encoder engine 106may entropy encode the vector. For example, the encoder engine 106 mayuse context adaptive variable length coding, context adaptive binaryarithmetic coding, syntax-based context-adaptive binary arithmeticcoding, probability interval partitioning entropy coding, or anothersuitable entropy encoding technique.

As previously described, an HEVC bitstream includes a group of NALunits, including VCL NAL units and non-VCL NAL units. VCL NAL unitsinclude coded picture data forming a coded video bitstream. For example,a sequence of bits forming the coded video bitstream is present in VCLNAL units. Non-VCL NAL units may contain parameter sets with high-levelinformation relating to the encoded video bitstream, in addition toother information. For example, a parameter set may include a videoparameter set (VPS), a sequence parameter set (SPS), and a pictureparameter set (PPS). Examples of goals of the parameter sets include bitrate efficiency, error resiliency, and providing systems layerinterfaces. Each slice references a single active PPS, SPS, and VPS toaccess information that the decoding device 112 may use for decoding theslice. An identifier (ID) may be coded for each parameter set, includinga VPS ID, an SPS ID, and a PPS ID. An SI'S includes an SPS ID and a VPSID. A PPS includes a PPS ID and an SPS ID. Each slice header includes aPPS ID. Using the IDs, active parameter sets can be identified for agiven slice.

A PPS includes information that applies to all slices in a givenpicture. Because of this, all slices in a picture refer to the same PPS.Slices in different pictures may also refer to the same PPS. An SPSincludes information that applies to all pictures in a same coded videosequence (CVS) or bitstream. As previously described, a coded videosequence is a series of access units (AUs) that starts with a randomaccess point picture (e.g., an instantaneous decode reference (IDR)picture or broken link access (BLA) picture, or other appropriate randomaccess point picture) in the base layer and with certain properties(described above) up to and not including a next AU that has a randomaccess point picture in the base layer and with certain properties (orthe end of the bitstream). The information in an SPS may not change frompicture to picture within a coded video sequence. Pictures in a codedvideo sequence may use the same SPS. The VPS includes information thatapplies to all layers within a coded video sequence or bitstream. TheVPS includes a syntax structure with syntax elements that apply toentire coded video sequences. In some embodiments, the VPS, SPS, or PPSmay be transmitted in-band with the encoded bitstream. In someembodiments, the VPS, SPS, or PPS may be transmitted out-of-band in aseparate transmission than the NAL units containing coded video data.

A video bitstream can also include Supplemental Enhancement Information(SEI) messages. For example, an SEI NAL unit can be part of the videobitstream. In some cases, an SEI message can contain information that isnot needed by the decoding process. For example, the information in anSEI message may not be essential for the decoder to decode the videopictures of the bitstream, but the decoder can be use the information toimprove the display or processing of the pictures (e.g., the decodedoutput). The information in an SEI message can be embedded metadata. Inone illustrative example, the information in an SEI message could beused by decoder-side entities to improve the viewability of the content.In some instances, certain application standards may mandate thepresence of such SEI messages in the bitstream so that the improvementin quality can be brought to all devices that conform to the applicationstandard (e.g., the carriage of the frame-packing SEI message forframe-compatible piano-stereoscopic 3DTV video format, where the SEImessage is carried for every frame of the video, handling of a recoverypoint SEI message, use of pan-scan scan rectangle SEI message in DVB, inaddition to many other examples).

The output 110 of the encoding device 104 may send the NAL units makingup the encoded video bitstream data over the communications link 120 tothe decoding device 112 of the receiving device. The input 114 of thedecoding device 112 may receive the NAL units. The communications link120 may include a channel provided by a wireless network, a wirednetwork, or a combination of a wired and wireless network A wirelessnetwork may include any wireless interface or combination of wirelessinterfaces and may include any suitable wireless network (e.g., theInternet or other wide area network, a packet-based network, WiFi™,radio frequency (RF), UWB, WiFi-Direct, cellular, Long-Term Evolution(LTE), WiMax™, or the like). A wired network may include any wiredinterface (e.g., fiber, ethernet, powerline ethernet, ethernet overcoaxial cable, digital signal line (DSL), or the like). The wired and/orwireless networks may be implemented using various equipment, such asbase stations, routers, access points, bridges, gateways, switches, orthe like. The encoded video bitstream data may be modulated according toa communication standard, such as a wireless communication protocol, andtransmitted to the receiving device.

In some examples, the encoding device 104 may store encoded videobitstream data in storage 108. The output 110 may retrieve the encodedvideo bitstream data from the encoder engine 106 or from the storage108. Storage 108 may include any of a variety of distributed or locallyaccessed data storage media. For example, the storage 108 may include ahard drive, a storage disc, flash memory, volatile or non-volatilememory, or any other suitable digital storage media for storing encodedvideo data. The storage 108 can also include a decoded picture buffer(DPB) for storing reference pictures for use in inter-prediction. In afurther example, the storage 108 can correspond to a file server oranother intermediate storage device that may store the encoded videogenerated by the source device. In such cases, the receiving deviceincluding the decoding device 112 can access stored video data from thestorage device via streaming or download. The file server may be anytype of server capable of storing encoded video data and transmittingthat encoded video data to the receiving device. Example file serversinclude a web server (e.g., for a website), an FTP server, networkattached storage (NAS) devices, or a local disk drive. The receivingdevice may access the encoded video data through any standard dataconnection, including an Internet connection. This may include awireless channel (e.g., a Wi-Fi connection), a wired connection (e.g.,DSL, cable modem, etc.), or a combination of both that is suitable foraccessing encoded video data stored on a file server. The transmissionof encoded video data from the storage 108 may be a streamingtransmission, a download transmission, or a combination thereof.

The input 114 of the decoding device 112 receives the encoded videobitstream data and may provide the video bitstream data to the decoderengine 116, or to storage 118 for later use by the decoder engine 116.For example, the storage 118 can include a DPB for storing referencepictures for use in inter-prediction. The receiving device including thedecoding device 112 can receive the encoded video data to be decoded viathe storage 108. The encoded video data may be modulated according to acommunication standard, such as a wireless communication protocol, andtransmitted to the receiving device. The communication medium fortransmitted the encoded video data can comprise any wireless or wiredcommunication medium, such as a radio frequency (RF) spectrum or one ormore physical transmission lines. The communication medium may form partof a packet-based network, such as a local area network, a wide-areanetwork, or a global network such as the Internet. The communicationmedium may include routers, switches, base stations, or any otherequipment that may be useful to facilitate communication from the sourcedevice to the receiving device.

The decoder engine 116 may decode the encoded video bitstream data byentropy decoding (e.g., using an entropy decoder) and extracting theelements of one or more coded video sequences making up the encodedvideo data. The decoder engine 116 may then rescale and perform aninverse transform on the encoded video bitstream data. Residual data isthen passed to a prediction stage of the decoder engine 116. The decoderengine 116 then predicts a block of pixels (e.g., a PU). In someexamples, the prediction is added to the output of the inverse transform(the residual data).

The decoding device 112 may output the decoded video to a videodestination device 122, which may include a display or other outputdevice for displaying the decoded video data to a consumer of thecontent. In some aspects, the video destination device 122 may be partof the receiving device that includes the decoding device 112. In someaspects, the video destination device 122 may be part of a separatedevice other than the receiving device.

In some embodiments, the video encoding device 104 and/or the videodecoding device 112 may be integrated with an audio encoding device andaudio decoding device, respectively. The video encoding device 104and/or the video decoding device 112 may also include other hardware orsoftware that is necessary to implement the coding techniques describedabove, such as one or more microprocessors, digital signal processors(DSPs), application specific integrated circuits (ASICs), fieldprogrammable gate arrays (FPGAs), discrete logic, software, hardware,firmware or any combinations thereof. The video encoding device 104 andthe video decoding device 112 may be integrated as part of a combinedencoder/decoder (codec) in a respective device. An example of specificdetails of the encoding device 104 is described below with reference toFIG. 10. An example of specific details of the decoding device 112 isdescribed below with reference to FIG. 11.

The example system shown in FIG. 1 is one illustrative example that canbe used herein. Techniques for processing video data using thetechniques described herein can be performed by any digital videoencoding and/or decoding device. Although generally the techniques ofthis disclosure are performed by a video encoding device or a videodecoding device, the techniques may also be performed by a combinedvideo encoder-decoder, typically referred to as a “CODEC.” Moreover, thetechniques of this disclosure may also be performed by a videopreprocessor. The source device and the receiving device are merelyexamples of such coding devices in which the source device generatescoded video data for transmission to the receiving device. In someexamples, the source and receiving devices may operate in asubstantially symmetrical manner such that each of the devices includevideo encoding and decoding components. Hence, example systems maysupport one-way or two-way video transmission between video devices,e.g., for video streaming, video playback, video broadcasting, or videotelephony.

Extensions to the HEVC standard include the Multiview Video Codingextension, referred to as MV-HEVC, and the Scalable Video Codingextension, referred to as SHVC. The MV-HEVC and SHVC extensions sharethe concept of layered coding, with different layers being included inthe encoded video bitstream. Each layer in a coded video sequence isaddressed by a unique layer identifier (ID). A layer ID may be presentin a header of a NAL unit to identify a layer with which the NAL unit isassociated. In MV-HEVC, different layers can represent different viewsof the same scene in the video bitstream. In SHVC, different scalablelayers are provided that represent the video bitstream in differentspatial resolutions (or picture resolution) or in differentreconstruction fidelities. The scalable layers may include a base layer(with layer ID=0) and one or more enhancement layers (with layer IDs=1,2, . . . n). The base layer may conform to a profile of the firstversion of HEVC, and represents the lowest available layer in abitstream. The enhancement layers have increased spatial resolution,temporal resolution or frame rate, and/or reconstruction fidelity (orquality) as compared to the base layer. The enhancement layers arehierarchically organized and may (or may not) depend on lower layers. Insome examples, the different layers may be coded using a single standardcodec (e.g., all layers are encoded using HEVC, SHVC, or other codingstandard). In some examples, different layers may be coded using amulti-standard codec. For example, a base layer may be coded using AVC,while one or more enhancement layers may be coded using SHVC and/orMV-HEVC extensions to the HEVC standard.

In general, a layer includes a set of VCL NAL units and a correspondingset of non-VCL NAL units. The NAL units are assigned a particular layerID value. Layers can be hierarchical in the sense that a layer maydepend on a lower layer. A layer set refers to a set of layersrepresented within a bitstream that are self-contained, meaning that thelayers within a layer set can depend on other layers in the layer set inthe decoding process, but do not depend on any other layers fordecoding. Accordingly, the layers in a layer set can form an independentbitstream that can represent video content. The set of layers in a layerset may be obtained from another bitstream by operation of asub-bitstream extraction process. A layer set may correspond to the setof layers that is to be decoded when a decoder wants to operateaccording to certain parameters.

As described above, for each block, a set of motion information (alsoreferred to herein as motion parameters) can be available. A set ofmotion information contains motion information for forward and backwardprediction directions. The forward and backward prediction directionsare two prediction directions of a bi-directional prediction mode, inwhich case the terms “forward” and “backward” do not necessarily have ageometrical meaning. Instead, “forward” and “backward” correspond toreference picture list 0 (RefPicList0 or L0) and reference picture list1 (RefPicList1 or L1) of a current picture. In some examples, when onlyone reference picture list is available for a picture or slice, onlyRefPicList0 is available and the motion information of each block of aslice is always forward.

In some cases, a motion vector together with its reference index is usedin coding processes (e.g., motion compensation). Such a motion vectorwith the associated reference index is denoted as a uni-predictive setof motion information. For each prediction direction, the motioninformation can contain a reference index and a motion vector. In somecases, for simplicity, a motion vector itself may be referred in a waythat it is assumed that it has an associated reference index. Areference index is used to identify a reference picture in the currentreference picture list (RefPicList0 or RefPicList1). A motion vector hasa horizontal and a vertical component that provide an offset from thecoordinate position in the current picture to the coordinates in thereference picture identified by the reference index. For example, areference index can indicate a particular reference picture that shouldbe used for a block in a current picture, and the motion vector canindicate where in the reference picture the best-matched block (theblock that best matches the current block) is in the reference picture.

A picture order count (POC) can be used in video coding standards toidentify a display order of a picture. Although there are cases forwhich two pictures within one coded video sequence may have the same POCvalue, it typically does not happen within a coded video sequence. Whenmultiple coded video sequences are present in a bitstream, pictures witha same value of POC may be closer to each other in terms of decodingorder. POC values of pictures can be used for reference picture listconstruction, derivation of reference picture set as in HEVC, and motionvector scaling.

In H.264/AVC, each inter macroblock (MB) may be partitioned in fourdifferent ways, including: one 16×16 MB partition; two 16×8 MBpartitions; two 8×16 MB partitions; and four 8×8 MB partitions.Different MB partitions in one MB may have different reference indexvalues for each direction (RefPicList0 or RefPicList1). In some cases,when an MB is not partitioned into four 8×8 MB partitions, it can haveonly one motion vector for each MB partition in each direction. In somecases, when an MB is partitioned into four 8×8 MB partitions, each 8×8MB partition can be further partitioned into sub-blocks, in which caseeach sub-block can have a different motion vector in each direction. Insome examples, there are four different ways to get sub-blocks from an8×8 MB partition, including: one 8×8 sub-block; two 8×4 sub-blocks: two4×8 sub-blocks; and four 4×4 sub-blocks. Each sub-block can have adifferent motion vector in each direction. Therefore, a motion vector ispresent in a level equal to higher than sub-block.

In AVC, a temporal direct mode can be enabled at either the MB level orthe MB partition level for skip and/or direct mode in B slices. For eachMB partition, the motion vectors of the block co-located with thecurrent MB partition in the RefPicList1[0] of the current block are usedto derive the motion vectors. Each motion vector in the co-located blockis scaled based on POC distances.

A spatial direct mode can also be performed in AVC. For example, in AVC,a direct mode can also predict motion information from the spatialneighbors.

As noted above, in HEVC, the largest coding unit in a slice is called acoding tree block (CTB). A CTB contains a quad-tree, the nodes of whichare coding units. The size of a CTB can range from 16×16 to 64×64 in theHEVC main profile. In some cases, 8×8 CTB sizes can be supported. Acoding unit (CU) could be the same size of a CTB and as small as 8×8. Insome cases, each coding unit is coded with one mode. When a CU isinter-coded, the CU may be further partitioned into 2 or 4 predictionunits (PUs), or may become just one PU when further partition does notapply. When two PUs are present in one CU, they can be half sizerectangles or two rectangles with % or % size of the CU.

When the CU is inter-coded, one set of motion information is present foreach PU. In addition, each PU is coded with a unique inter-predictionmode to derive the set of motion information.

For motion prediction in HEVC, there are two inter-prediction modes,including merge mode and advanced motion vector prediction (AMVP) modefor a prediction unit (PU). Skip is considered as a special case ofmerge. In either AMVP or merge mode, a motion vector (MV) candidate listis maintained for multiple motion vector predictors. The motionvector(s), as well as reference indices in the merge mode, of thecurrent PU are generated by taking one candidate from the MV candidatelist.

In some examples, the MV candidate list contains up to five candidatesfor the merge mode and two candidates for the AMVP mode. In otherexamples, different numbers of candidates can be included in a MVcandidate list for merge mode and/or AMVP mode. A merge candidate maycontain a set of motion information. For example, a set of motioninformation can include motion vectors corresponding to both referencepicture lists (list 0 and list 1) and the reference indices. If a mergecandidate is identified by a merge index, the reference pictures areused for the prediction of the current blocks, as well as the associatedmotion vectors are determined. However, under AMVP mode, for eachpotential prediction direction from either list 0 or list 1, a referenceindex needs to be explicitly signaled, together with an MVP index to theMV candidate list since the AMVP candidate contains only a motionvector. In AMVP mode, the predicted motion vectors can be furtherrefined.

As can be seen above, a merge candidate corresponds to a full set ofmotion information, while an AMVP candidate contains just one motionvector for a specific prediction direction and reference index. Thecandidates for both modes are derived similarly from the same spatialand temporal neighboring blocks.

In some examples, merge mode allows an inter-predicted PU to inherit thesame motion vector or vectors, prediction direction, and referencepicture index or indices from an inter-predicted PU that includes amotion data position selected from a group of spatially neighboringmotion data positions and one of two temporally co-located motion datapositions. For AMVP mode, motion vector or vectors of a PU can bepredicatively coded relative to one or more motion vector predictors(MVPs) from an AMVP candidate list constructed by an encoder. In someinstances, for single direction inter-prediction of a PU, the encodercan generate a single AMVP candidate list. In some instances, forbi-directional prediction of a PU, the encoder can generate two AMVPcandidate lists, one using motion data of spatial and temporalneighboring PUs from the forward prediction direction and one usingmotion data of spatial and temporal neighboring PUs from the backwardprediction direction.

As previously described, various prediction modes may be used in a videocoding process, including intra-prediction and inter-prediction. Oneform of intra-prediction includes intra-block copy (IBC). IBC can alsobe referred to as Current Picture Referencing (CPR). IBC (or CPR) wasproposed during the standardization of the HEVC screen content coding(SCC) extensions. IBC has been proven to be efficient when coding ofscreen content video materials, and can also be used to code other videocontent. The IBC/CPR method was proposed in JVET-J0029 and JVET-J0050 toaddress the need for efficient screen content coding. In the 11^(th)JVET meeting, IBC/CPR mode was adopted into Benchmark Set (BMS) softwarefor further evaluation.

In IBC mode, an intra-block copy block is predicted from one or morealready decoded blocks (e.g., before in-loop filtering) of the currentpicture (see FIG. 2 and FIG. 3). The term in-loop filtering here mayinclude using deblocking (DB) filtering, an Adaptive Loop Filter (ALF),and/or Sample Adaptive Offset (SAO) filtering. Using redundancy in animage picture or frame, IBC performs block matching to predict a blockof samples (e.g., a CU, a PU, or other coding block) as a displacementfrom a reconstructed block of samples in a neighboring or anon-neighboring region of the picture. By removing the redundancy fromrepeating patterns of content, the intra-block copy prediction improvescoding efficiency.

In some implementations of IBC, block compensation can be performed. Forexample, in some cases, for the luma blocks that are coded with IBC/CPR,prediction of the luma blocks can include block compensation. Forinstance, integer block compensation can be applied to the predictedluma blocks, in which case interpolation is not needed. In someexamples, block compensation can also be performed for chroma blocks. Insome implementations, block compensation for chroma blocks can includesub-pel block compensation which would also involve interpolation.

In various examples, IBC prediction (e.g., by an encoding device and/ora decoding device when in an IBC mode) can enable spatial predictionfrom non-neighboring samples of a block where the non-neighboringsamples are located within a current picture. For example, FIG. 2illustrates a coded picture 200 in which IBC prediction is used topredict a current coding unit 202. The coding unit 202 can include a CTUor a partition of a CTU (e.g., a coding unit (CU) containing luma andchroma sample arrays referred to as coding blocks, a coding block, aprediction unit (PU) containing a luma prediction block (PB) and one ormore chroma PBs, a prediction block, or other partition including ablock of pixels). The current coding unit 202 is predicted from analready decoded prediction block 204 (e.g., in some cases, beforein-loop filtering) of the coded picture 200 using the block vector 206.In-loop filtering may be performed using one or more of an in-loopde-blocking filter, an ALF, and/or an SAO filter. In some cases, in thedecoding loop (of an encoder and/or decoder), the predicted values canbe added to the residues without any interpolation. For example, theblock vector 206 may be signaled as an integer value. After block vectorprediction, the block vector difference is encoded using a motion vectordifference coding method, such as that specified in the HEVC standard.In some cases, IBC is enabled at both CU and PU level. In someinstances, for PU level IBC, 2N×N and N×2N PU partition is supported forall the CU sizes. In some cases, when the CU is the smallest CU, N×N PUpartition is supported. In some examples, intra-block copy can beperformed for a coding unit using only prediction blocks from a sameslice.

FIG. 3 is a block diagram which provides another illustration of the IBCmode. In FIG. 3, a picture 300 is shown, where one or more blocks of thepicture 300 can be coded using IBC prediction or other prediction. Insome examples, the one or more blocks of the picture 300 can be coded inan order, such as row by row starting from a top left corner andproceeding towards the bottom right corner of the picture 300. In suchexamples, the picture 300 can have one or more previously coded blocksto the left and/or top of a current block to be coded. For example,considering a current block 302 which is to be coded, the picture 300can include previously coded blocks in a region of the picture 300 whichincludes blocks to the left of the current block 302 and/or blocks abovethe current block 302. This region which includes the previously codedblocks can form a search region 308 for the current block 302 forperforming IBC prediction of the current block 302.

For example, the current block 302 can include a current CU (or PU) tobe coded using IBC prediction. In some examples, a previously or alreadydecoded prediction block 304 can be found for IBC prediction of thecurrent block 302 by searching for the prediction block 304 in thesearch region 308. If such a prediction block 304 is found, then a blockvector 306 can be generated to identify a location of the predictionblock 304 relative to the location of the current block 302 in thepicture 300. For example, the block vector 306 can be encoded using amotion vector difference coding such as that specified in the HEVCstandard. In some examples, a prediction signal for IBC prediction ofthe current block 302 can be generated using the prediction block 304and the block vector 306. In some examples, a larger area of the searchregion 308 can improve the chances of locating a prediction block suchas the prediction block 304 for IBC prediction of the current block 302.In some examples, the reconstructed pixels of the previously decodedblocks in the search region 308 are stored in a physical memory. In someexamples, searching for the prediction block 304 for IBC prediction ofthe current block can include searching the physical memory to locatethe previously decoded the prediction block 304. In some examples, thephysical memory can include a circular buffer, a line buffer, or otherstorage space which may be available for encoding or decoding thepicture 300.

In some IBC implementations, a pipelined approach can be used where eachCTU being coded can be divided into multiple units and processed in astepwise manner. In some examples, the pipelined approach can enablereuse of resources. For example, physical memory such as the samecircular buffer and/or other computational resources can be used fortemporary storage of coding information related to one or more of themultiple units being processed. For example, a portion of the storagespace in the circular buffer can be freed up after processing one unitto make room for processing another unit. In some examples, the multipleunits processed in the pipelined approach can include virtual pipelinedata units (VPDUs).

In some examples, VPDUs can include non-overlapping cells in a pictureor video frame. For example, VPDUs can be non-overlapping M×M-luma(L)/N×N-chroma (C) units in a picture. The VPDU construct includesvirtual blocks that are used for memory access (e.g., to determine whicharea of memory is used for processing a particular block or blocks ofdata), defining the size of the memory allocated to implement aStandard-based coding process (e.g., HEVC, VVC, or other codingprocess). In some examples of a hardware decoding process, consecutiveVPDUs can be processed in parallel by multiple processing/decodingpipeline stages. For example, different decoding pipeline stages canprocess different VPDUs simultaneously. In some cases, a VPDU size canbe roughly proportional to the buffer size in some pipelines. Forinstance, a VPDU size can be set to the size of a transform block (TB)size. In one illustrative example, the size of a VPDU can be 64×64samples (e.g., luma samples). In HEVC, the VPDU size is set to maximumtransform block size which is 32×32-L (Luma samples) and 16×16-C (Chromasamples). In VVC, the VPDU size is set to 128×128-L (Luma samples) and64×64-C (Chroma samples), which results in the request of larger VPDUsizes.

A VPDU can include one or more blocks (e.g., a CU, PU, TU, or otherblock). For example, in some cases, a single CU can be included in oneVPDU (e.g., the size of the CU and the VPDU size are the same). In somecases, multiple CUs can be included in one VPDU (e.g., the multiple CUshave sizes that are smaller than the VPDU size). Depending on the sizeof a block (e.g., a CU, PU, or other block), the block may or may notspan multiple VPDUs (in which case a block may include multiple VPDUs).For example, a block having a size of 128×64 (128 samples wide×64samples high) can span two VPDUs that each have a size of 64×64. Inanother example, a block having a size of 128×128 (128 samples wide×128samples high) can span four VPDUs that each have a size of 64×64. Theblock can be split into a certain number of sub-blocks for performinginter-prediction by each of the VPDU pipeline stages. For example, a128×128 block can be split into for 64×64 sub-blocks for processing byfour different VPDU pipeline stages. The block can be split forinter-prediction because there is no dependency on neighboring blocksfor performing inter-prediction.

FIG. 4 is a diagram illustrating an example of coding unit 400 which caninclude one or more blocks of a picture of video data. The coding unit400 can be divided into two or VPDUs to be processed in a pipelinedmanner. For example, the coding unit 400 can include a 128×128 CTU (128samples by 128 samples), which can be divided or split into four 64×64VPDUs: VPDU0, VPDU1, VPDU2, and VPDU3. In some examples, a circularbuffer can provide storage space for processing video data contained inthe coding unit 400. For example, a portion of the circular buffer canbe used for temporarily storing motion information related to one ormore blocks of one of the VPDUs (e.g., VPDU0) for a period of time(e.g., for a pipeline stage duration). For a subsequent period of time(e.g., a subsequent pipeline stage), the portion of the circular buffercan be made available for temporarily storing motion information relatedto one or more blocks of another one of the VPDUs (e.g., VPDU1). In thismanner, the same portion of the circular buffer can be utilized for apipelined processing of the two or more VPDUs, such as VPDU0-VPDU3 ofthe coding unit 400 (and/or for VPDUs of other coding units). In someexamples, the circular buffer can be implemented as a first-in-first-out(FIFO) buffer.

Accordingly, in various examples, a limited amount of storage space maybe available for storing information related to processing video data.The storage space restrictions can lead to problems in implementing IBC,among other inter-prediction and/or intra-prediction techniques. Forexample, as previously explained, IBC allows spatial prediction fromnon-neighboring samples which can include previously decoded blocksbefore in-loop filtering is applied. The previously decoded blocks arelocated within the same picture and can be signaled by a block vector.For example, reconstructed pixels (before filtering in some cases) ofpreviously decoded prediction blocks within a search region can bestored and used for performing a search of the search region in IBCprediction of a current block. Storing unfiltered reconstructed pixelsconsumes more storage space, memory bandwidth, and processing resourceutilization in comparison to storing filtered reconstructed pixels.

Furthermore, accessing such non-neighboring samples from memory canincrease the memory bandwidth consumption and memory access times. Forexample, in the case of conventional intra-prediction mode, neighboringsamples located one row above or one column to the left of a currentblock can be used in the prediction of the current block. Thus, theseneighboring samples may be stored in a local memory or cache based ontheir likelihood of being accessed in the near future for prediction ofthe current block. However, since IBC can search for previously decodedblocks which can include non-neighboring samples, such non-neighboringsamples may not be located in the cache or local memory at the time thatthey may be accessed for IBC prediction of the current block. Rather,the non-neighboring samples may be stored in longer term memorylocations which may be further away from the local memory. Thus,fetching the non-neighboring samples can involve increased read accesstimes for fetching the non-neighboring samples from non-local memory orcache. In addition to the increased storage space for storing thenon-neighboring samples, the duration of time for which thenon-neighboring samples are to be stored can also be high. For example,the non-neighboring samples may be accessed for IBC prediction of acurrent block after a significant amount of time has lapsed since thetime the non-neighboring samples were generated. Accordingly, in orderto support the increased number of non-neighboring samples to be madeavailable for searching with smaller access times, the IBC mode mayplace demands on additional fast-access storage space, such as largerlocal memory structures or caches.

Furthermore, when performing IBC, increased write access is caused due,in part, to the storage of both unfiltered samples (e.g., a predictionblock) for IBC-based spatial prediction and filtered reconstructedsamples for temporal prediction for future pictures (e.g., usinginter-prediction). Thus, there may also be a further increase in thedemand for storage space for storing the unfiltered samples as well asthe filtered samples that are generated during in-loop filtering.

Some approaches for addressing the increased demands on storage spacefor IBC include placing restrictions on the search area for locating theprediction block to be used for IBC prediction of a current block. Forexample, referring to FIG. 3, the search region 308 for locating thecurrent block 304 for IBC prediction of the current block 302 can berestricted. For example, the search region 308 can be limited to includea search region corresponding to storage space that would be equal tothe storage space for storing samples of one CTU (referred to as “CTUstorage”). For example, the total storage made available for IBCprediction of the current block 302 can be limited to one CTU storagespace, placing a corresponding limitation on the search region 308.However, restricting the search region 308 to be limited by one CTUstorage space can impact performance of IBC coding. For example, theperformance of IBC coding is seen to improve when a larger search areais made available for locating the prediction block 304. In someexamples, one CTU storage can include reconstructed pixels within acurrent CTU that includes the current block 302. In some examples, oneCTU storage can include reconstructed pixels from both a leftneighboring CTU and the current CTU (e.g., a portion of the pixels fromthe left neighboring CTU and a portion of the pixels from the currentCTU).

In some examples where a circular buffer may be used for pipelinedprocessing, the one CTU storage restriction can be implemented byreusing a portion of the circular buffer for storing newly reconstructedpixels for the current CTU, where that portion was previously utilizedfor storing reconstructed pixels of a previous CTU. In some examples ofimplementing the circular buffer, the portion can be updated in a unitby unit manner, with an update rate for a unit being based on acorresponding pipeline stage's throughput. For example, the update ratecan be one pixel, four pixels, 2×2 pixels, 4×4 pixels, the whole virtualpipeline data unit (VPDU), or other number of pixels.

One or more systems and methods of coding are described herein thatprovide performance improvements and complexity reduction to the IBC/CPRmode. For example, techniques described herein address the problemsassociated with storage space utilized for the IBC prediction. In someexamples, the problems associated with storage space restrictions can beovercome using a virtual search area (VSA). In some examples, thevirtual search area can include one or more references to one or morepixels stored in a physical memory. For example, the virtual search areacan provide a reference to additional reconstructed sample values thatare derived from previously decoded blocks without incurring physicalmemory use for storage of the additional reconstructed samples.

In some examples, the virtual search area can include one or morereferences to one or more pixels stored in the physical memory, wherethe one or more references can effectively constitute pixel paddingwithout incurring pixel storage space in the physical memory for thepadded pixels. The search area for performing the IBC prediction for acurrent block can be extended to include the virtual search area (e.g.,the padding pixels of the virtual search area). For example, the virtualsearch area can provide additional reconstructed samples from previouslydecoded blocks without incurring physical memory use for the additionalreconstructed samples. In some examples, extending the search area toinclude the virtual search area provides the IBC prediction beingperformed for the current block with additional search area (i.e.,search area being virtual in that pixel values within the search areaare not stored in physical memory) for finding a prediction block orprediction samples without having to utilize physical memory to storethe additional reconstructed samples from previously decoded blocksreferenced above.

FIG. 5 is a block diagram illustrating virtual search areas for a CTU inaccordance with some examples. A picture 500 of video data can includeone or more coding blocks, such as a coding block identified as acurrent CTU 510. In some examples, the coding block identified by thereference numeral 510 can include other block sizes or data units, suchas a VPDU. In an example, a current block 502 of the current CTU 510 caninclude a CU/PU to be coded using IBC prediction. According toconventional techniques discussed above, the search area for locating apreviously decoded prediction block for the IBC prediction of thecurrent block 502 can be restricted to one CTU storage based on storagespace constraints. However, to avoid the negative effects of suchrestrictions, the search area can be extended beyond the one CTU storageusing example techniques disclosed herein.

In some examples, the search area for the IBC prediction of the currentblock 502 can be extended beyond the current CTU 510 to include one ormore virtual search areas 506 a, 506 b, 506 c, and/or other virtualsearch areas. In some examples, the one or more virtual search areas caninclude references to reconstructed pixels of one or more previouslydecoded blocks. For example, the references can include mappings,indices, and/or pointers to storage locations where the reconstructedpixels of one or more previously decoded blocks are stored. In someexamples, the one or more virtual search areas can include a predefinedfixed pattern, such as a row and/or column of pixels of value “0” or “1”or other pattern. In some examples, the references can include any otherindications to storage locations without including the values stored inthe storage locations. In some cases, the one or more virtual searchareas are said to include a padding, where the padding, as used herein,provides a pixel value which can be searched without consuming storingspace for the pixel values.

In some examples, the virtual search area 506 a can be formed by usingreferences to previously reconstructed pixels belonging to a boundary504 a (e.g., top boundary) of the current CTU 510. For example, thevirtual search area 506 a can include padding values that are referencesto reconstructed pixels of previously decoded blocks belonging to theboundary 504 a. In some examples, the reconstructed pixels belonging tothe boundary 504 a may be stored in a physical memory such as a linebuffer, a circular buffer, a ping pong buffer, or other memorystructure. The padding values can point to locations in the physicalmemory where these previously reconstructed pixels of the previouslydecoded blocks are stored. In some examples, two or more padding valuescan point to the same decoded block such that the same pixel value canbe repeated multiple times within a virtual search area, withoutincreasing the amount of storage in the physical memory. In someexamples, a multiple can be assigned to a stored pixel in the physicalmemory. Using the multiple assigned to the stored pixel, a searchalgorithm for the IBC can be configured to consider the stored pixelmultiple times in finding a prediction block for the current block 502.For example, multiple references to a row of reconstructed pixelsbelonging to the boundary 504 a can effectively generate the virtualsearch area 506 a with the row of reconstructed pixels being repeatedmultiple times in the virtual search area 506 a. Thus, the row ofreconstructed pixels can be made available for searching multiple times,potentially improving the likelihood of a prediction block belonging tothe row of pixels in the boundary 504 a being found in the virtualsearch area 506 a.

The virtual search area 506 b can be similarly formed using referencesto previously reconstructed pixels belonging to a boundary 504 b (e.g.,left boundary) of the current CTU 510. For example, the virtual searcharea 506 b can be padded with multiple references to reconstructedpixels belonging to the boundary 504 b. The reconstructed pixelsbelonging to the boundary 504 b may similarly be stored in a physicalmemory such as a line buffer or a circular buffer. The padding withmultiple references to the reconstructed pixels belonging to theboundary 504 b can effectively make the reconstructed pixels belongingto the boundary 504 b available for searching multiple times, thuspotentially increasing the likelihood of a prediction block being foundin the virtual search area 506 b.

The virtual search area 506 c can be formed using references topreviously reconstructed pixels belonging to the boundary 504 a, theboundary 504 b, or any other previously reconstructed pixels. Similar tothe virtual search areas 506 a and 506 b, the virtual search area 506 c_([TH1]) can include padding with multiple references to reconstructedpixels belonging a boundary or other reconstructed pixels of previouslydecoded blocks of the current CTU 510. In some examples, the virtualsearch area 506 c can also include a predefined fixed pattern. Forexample, the predefined fixed pattern can include a pattern formed usingthe bits “0” and/or “1”. In some examples of using a predefined fixedpattern, an encoding device as well as a decoding device can generatethe virtual search area 506 c using the same predefined fixed pattern.Accordingly, in some examples, the virtual search area 506 c can begenerated using padding values which may not be derived fromreconstructed pixels of previously decoded blocks. In various examples,the padding values in the virtual search area 506 c can potentiallyincrease the likelihood of a prediction block being found in the virtualsearch area 506 c.

In some cases, the virtual search areas 506 a-506 c can each include asearch area which is comparable in size to the size of current CTU 510(e.g., in terms of the number of pixels referenced by the virtual searchareas 506 a-c). In some cases, the virtual search areas 506 a-506 c orother such padding can be extended indefinitely (e.g., to infinity), ifno other constraint is applied. In some examples, the one or morevirtual search areas 506 a-506 c can be generated using the referencesto the reconstructed pixels. For example, an encoding device configuredto implement IBC prediction, such as the encoding device 104 of FIG. 10,can generate the one or more virtual search areas 506 a-506 c. Theencoding device can encode the references to the reconstructed pixelsused in generating the one or more virtual search areas 506 a-506 c. Theencoding (or coding) can include a reconstructed pixel being assigned toone or more padding values, or one or more references to thereconstructed pixel being generated. The one or more references caninclude pointers or mappings to a storage location where thereconstructed pixel has been previously stored, without incurringadditional storage space for the reconstructed pixel. In some examples,if a virtual search area includes multiple references to the samereconstructed pixel, the multiple references can be efficiently coded toinclude the multiple in the coding. In some examples, the one or morevirtual search areas can be signaled (e.g., to a decoding device such asthe decoding device 112 of FIG. 11), where the signaling can include thereferences and the multiple which indicates the number of times thereconstructed pixels are to be repeated.

In some examples, it is possible for a prediction block to be partiallylocated outside a search area, where a portion of the prediction blockis located within the search area and another portion of the predictionblock is located outside the search area. For example, a predictionblock which includes a CU/PU may not belong entirely within the currentCTU 510, with a portion of the prediction block being located inside ofthe current CTU 510 a and a portion of the prediction block beinglocated outside the current CTU 510. In some implementations, a searchfor prediction blocks within the current CTU 510 can be constrained toinclude searching only the prediction blocks which are entirely withinthe current CTU 510. For example, the search could be limited to astorage space which includes reconstructed pixels of previously decodedblocks which are entirely within the current CTU 510. In such examples,the prediction block which is partially located outside the current CTU510 may be excluded from the search. In example implementations, one ormore virtual search areas can include references to such predictionblocks even if they are partially located outside the current CTU 510.For instance, one or more padding pixels can be used to virtuallyrepresent the pixels from the prediction block that are outside of thecurrent CTU 510, allowing the prediction block to be included in thesearch and potentially used for IBC. For example, one or more paddingvalues of one or more virtual search areas 506 a-506 c can include areference to a storage location where the prediction block is stored,even if the storage location is not entirely within a storage spaceallocated for the current CTU 510. In this way, the one or more virtualsearch areas 506 a-506 c can allow a search for prediction blocks whichmay not be entirely located within the current CTU 510.

FIG. 6 is a block diagram illustrating virtual search areas and make upareas for a CTU in accordance with some examples. A picture 600 of videodata can include one or more coding blocks such as a current CTU 610.The search area for coding blocks of the current CTU 610 using IBC canbe extended beyond the current CTU 610 using one or more virtual searchareas 606 a, 606 b, 606 c, and/or other search areas. In some examples,the reconstructed pixels of neighboring CTUs of the current CT 610 canbe used for constructing the one or more virtual search areas 606 a, 606b, 606 c. For example, previously reconstructed pixels belonging to aboundary 604 a of a top neighboring CTU can be stored in a physicalmemory such as a line buffer. The virtual search area 606 a can includeone or more references to the storage locations (e.g., in the linebuffer) of the previously reconstructed pixels of the boundary 604 a.Similarly, previously reconstructed pixels belonging to a boundary 604 bof a left neighboring CTU can be stored in a physical memory such as thesame or a different line buffer than the one in which the reconstructedpixels of the boundary 604 a are stored. The virtual search area 606 bcan include one or more references to the storage locations of thepreviously reconstructed pixels belonging to the boundary 604 b.

In addition to or as an alternative to the one or more references to thepreviously reconstructed pixels of neighboring CTUs, the virtual searchareas 606 a and 606 b can also include references to previouslyreconstructed pixels belonging to boundaries of the current CTU 610(e.g., top boundary and/or left boundary of the current CTU 610).

The virtual search area 606 c can be formed using references topreviously reconstructed pixels belonging to the boundary 604 a of theleft neighboring CTU, the boundary 604 b of the top neighboring CTU, atop boundary of the current CTU 610, a left boundary of the current CTU610, a combination of one or more of the above reconstructed pixels, orany other “made up” value, including values obtained from previouslyreconstructed pixels of the current CTU 610. In this disclosure, a “madeup” value can refer to a pixel value that has been used for padding inthe extending the search area, where the pixels or values referred to bythe made up values do not consume additional storage space. In someexamples, the made up values can refer to constant values or otherreferences. In some examples, the made up values included in the virtualsearch area 606 c can increase the likelihood of a prediction block forIBC of a block of the current CTU 610 being found in the virtual searcharea 606 c.

FIG. 7A and FIG. 7B are block diagrams which illustrate the use ofvirtual search areas and circular buffers for IBC prediction. Forexample, FIG. 7A illustrates a current CTU 710 of a picture 700 of videodata, where the current CTU 710 can include one or more blocksconfigured to be predicted using IBC prediction. The current CTU 710 canbe divided into two or more virtual pipeline data units (VPDUs) forprocessing in a pipelined manner using shared resources such as acircular buffer. In an illustrative example, one of the two or moreVPDUs of the current CTU 710 can include VPDU0 whose blocks may be in acurrent pipeline stage of processing for IBC prediction. For example, aportion of the circular buffer may be temporarily reserved and used forprocessing and updating blocks of VPDU0 during the current pipelinestage. In an example, a current block 702 of the VPDU0 can include a CUor a PU to be coded using IBC prediction. For example, IBC prediction ofthe current block 702 can include searching for a prediction block amongpreviously decoded blocks of VPDU0 (among other previously decodedblocks, such as those in virtual search areas as previously explained).In some examples, the reconstructed pixels of one or more blocks ofVPDU0 may be stored in the circular buffer while IBC prediction is beingperformed on one or more blocks of the VPDU0. For example, thereconstructed pixels of the previously decoded blocks of VPDU0 can bestored in the portion of the circular buffer during the current pipelinestage when IBC prediction of the current block 702 is being performed.

However, searching through the stored reconstructed pixels of one ormore previously decoded blocks of VPDU0 (at the same time that one ormore other blocks of VPDU0 are being processed introduces complexities.For example, searching through previously decoded blocks of VPDU0 in theportion of the circular buffer for IBC prediction of the current block702 is difficult because the searching can involve reading the storedbeing performed in parallel with other operations. For example, theother operations can include contents (e.g., reconstructed pixels ofother blocks) being written to the portion of the circular buffer.Supporting multiple simultaneous reads and writes to the same oroverlapping regions of physical memory can involve complex and expensivehardware designs among other challenges. Therefore, it is desirable toavoid searching through the portion of the circular buffer reserved forprocessing a VPDU at the same time that one or more blocks of the VPDUare being processed. For example, it is desirable to disallow or preventsearching through the portion of the circular buffer reserved for VPDU0when IBC prediction is being performed on one or more blocks such as thecurrent block 702 of the VPDU0.

In some examples, a virtual search area may be provided to overcome therestriction of the previously decoded blocks of VPDU0 being unavailablefor searching while VPDU0 is being processed (e.g., for IBC predictionof the current block 702). For example, FIG. 7B is a block diagramillustrating a circular buffer 720. In some examples, the circularbuffer 720 can be used for storing information for two or more VPDUs atthe same time. For example, the circular buffer 720 can storereconstructed pixels of VPDU0 in a portion 706 while VPDU0 is beingprocessed. Another portion 712 of the circular buffer 720 can be usedfor storing information for one or more other VPDUs, such asreconstructed pixels of one or more VPDUs belonging to a neighboring CTUto the left of the current CTU 710 (e.g., an immediately-adjacent CTU tothe left of the current CTU 710). In some examples, since the portion706 reserved for the VPDU0 of the current CTU 710 may be unavailable forsearching during IBC prediction of one or more blocks of VPDU0, avirtual search area can be provided for IBC prediction of the one ormore blocks of VPDU0. In some examples, the virtual search area caninclude references to one or more reconstructed pixel values ofpreviously decoded blocks of other VPDUs (e.g., of the current CTU 710or other CTU) or made up pixel values.

In some examples, a virtual search area can be used if the availablesearch area for one or more blocks of a coding unit are constrained inanother manner. For example, if the search area available for a CTU isconstrained to include previously decoded pixels of an area smaller thanthe CTU, then one or more virtual search areas can be used to extend theavailable search area. For example, if the search area for a 128×128 CTUis constrained to include a search area corresponding to that of a 64×64VPDU, then one or more virtual search areas such as those describedabove can be used to extend the search area beyond the 64×64 VPDU searcharea.

In the various examples discussed herein, the one or more virtual searchareas for IBC/CPR can lead to improvements in coding performance withoutincreasing the storage cost. In some examples, the one or more virtualsearch areas for IBC/CPR can enable a regular shape (e.g., a rectangularshape) for the search area, even if an available search area is anirregular shape. A regular shaped search area can enable maintainingcontinuous motion estimation without breaks which can be introduced dueto irregular shaped search areas.

FIG. 8 is a flowchart illustrating an example of a process 800 ofencoding video data by extending a search area for performingintra-block copy (IBC) prediction of a block of video data, using one ormore virtual search areas. At block 802, the process 800) includesobtaining a current block of a picture of video data. In some examples,the video data can include un-encoded video data, such as when theprocess 800 is performed by an encoding device. The video data caninclude a plurality of pictures, and the pictures can be divided into aplurality of blocks, as previously described. The process 800 candetermine motion information for the pictures and/or blocks, which canbe used to perform motion compensation.

At 804, the process 800 includes generating a virtual search area forperforming intra-block copy prediction for a current block of the videodata, the virtual search area including one or more references to one ormore pixels stored in a physical memory. For example, as shown in FIG.5, one or more virtual search areas 506 a-c can be generated forperforming intra-block copy prediction for the current block 502 of thevideo data. The current block 502 can include a CU or PU and can belongto a current CTU 510. In some examples, the virtual search areas 506 a-ccan include one or more references to one or more pixels stored in aphysical memory.

In some examples, the physical memory can include a circular buffer or aping pong buffer for storing reconstructed pixels of a coding unitincluding one or more blocks of the video data. For example, thecircular buffer 720 can be configured to store reconstructed pixels of acoding unit including the current block 702 as shown in FIG. 7. In someexamples, the coding unit can include two or more virtual pipeline dataunits (VPDUs), such as VPDU0-VPDU3 as shown in the coding unit or CTU400 of FIG. 4. In some examples, at least one VPDU of the two or moreVPDUs can include the current block. For example, the VPDU0 can includethe current block 702.

In some examples, the physical memory can include a line buffer forstoring reconstructed pixels of one or more blocks of the video data.For example, the physical memory can include a line buffer for storingreconstructed pixels of one or more blocks belonging to a neighboringcoding unit of the current CTU including the current block. For example,the physical memory can include a line buffer for storing reconstructedpixels of one or more blocks belonging to the boundary 604 a of a topneighboring CTU of the current CTU 610 and/or the boundary 604 b of aleft neighboring CTU of the current CTU 610. In some examples, thevirtual search area 606 a can include one or more references to the oneor more pixels of the boundary 604 a stored in the line buffer, and thevirtual search area 606 b can include one or more references to the oneor more pixels of the boundary 604 b stored in the line buffer.

At 806, the process 800 includes extending a search area for performingthe intra-block copy prediction for the current block to include thevirtual search area. For example, the search area for performing theintra-block copy prediction for the current block 502 in FIG. 5 can beextended to include the one or more virtual search areas 506 a-506 c. Insome examples, the intra-block copy prediction for the current block 502can be performed using one or more references to one or more pixels inthe one or more virtual search areas 506 a-506 c.

At block 808, the process 800 includes generating an encoded bitstreamincluding at least a portion of the current block. In some examples,information for generating one or more virtual search areas 506 a-506 cfor the current block 502 can also be included in the encoded bitstream.For example, a predefined fixed bit pattern or made up padding valuesfor the virtual search area 506 c as discussed above can be signaledfrom the encoding device to a decoding device in the encoded bitstream.In some examples, the one or more virtual search areas for the currentblock can be generated by the decoding device using reconstructed pixelsof one or more decoded blocks, upon obtaining the current block from theencoded bitstream.

FIG. 9 is a flowchart illustrating an example of a process 900 ofdecoding video data by extending a search area for performingintra-block copy (IBC) prediction of a block of video data, using one ormore virtual search areas. At 902, the process 900 includes obtaining anencoded video bitstream including the video data. In some examples, theprocess of obtaining the encoded video bitstream can be performed by adecoding device. The video data can include a plurality of pictures, andthe pictures can be divided into a plurality of blocks, as previouslydescribed. The video data can also include motion information for thepictures and/or blocks, which can be used to perform motioncompensation.

At 904, the process 900 includes generating a virtual search area forperforming intra-block copy prediction for a current block of the videodata, the virtual search area including one or more references to one ormore pixels stored in a physical memory. For example, as shown in FIG.5, one or more virtual search areas 506 a-c can be generated forperforming intra-block copy prediction for the current block 502 of thevideo data. The current block 502 can include a CU or PU and can belongto a current CTU 510. In some examples, the virtual search areas 506 a-ccan include one or more references to one or more pixels stored in aphysical memory.

For example, the one or more pixels stored in the physical memory caninclude reconstructed pixels belonging to a boundary 504 a or a boundary504 b of the current CTU 510 or other coding unit. In some examples, theone or more references to the one or more pixels stored in the physicalmemory can include repeated references to the reconstructed pixelsbelonging to the boundary. For example, the virtual search area 506 acan include repeated references to the reconstructed pixels belonging tothe boundary 504 a and the virtual search area 506 b can includerepeated references to the reconstructed pixels belonging to theboundary 504 b of the current CTU 510. In some examples, the repeatedreferences to the reconstructed pixels belonging to the boundary 504 acan include a first reference to at least one reconstructed pixelbelonging to the boundary 504 a and a second reference to the at leastone reconstructed pixel belonging to the boundary 504 a. Similarly, therepeated references to the reconstructed pixels belonging to theboundary 504 b can include a first reference to at least onereconstructed pixel belonging to the boundary 504 b and a secondreference to the at least one reconstructed pixel belonging to theboundary 504 b. In some examples, the one or more references to the oneor more pixels can include made up values such as those shown in thevirtual search area 606 c of FIG. 6.

In some examples, the physical memory can include a circular buffer forstoring reconstructed pixels of a coding unit including one or moreblocks of the video data. For example, the circular buffer 720 can beconfigured to store reconstructed pixels of a coding unit including thecurrent block 702 as shown in FIG. 7. In some examples, the coding unitcan include two or more virtual pipeline data units (VPDUs), such asVPDU0-VPDU3 as shown in the coding unit or CTU 400 of FIG. 4. In someexamples, at least one VPDU of the two or more VPDUs can include thecurrent block. For example, the VPDU0 can include the current block 702.In some examples, at least a portion of the circular buffer can beconfigured to store reconstructed pixels of the at least one VPDU whileintra-block copy prediction is being performed on the one or more blocksof the at least one VPDU. For example, the portion 706 of the circularbuffer 720 can be configured to store reconstructed pixels of the VPDU0while intra-block copy prediction is being performed on the currentblock 702 of the VPDU0.

In some examples, at least the portion of the circular buffer being usedstoring reconstructed pixels of the at least one VPDU while intra-blockcopy prediction is being performed on the one or more blocks of the atleast one VPDU is unavailable for storing pixels of the search area forperforming the intra-block copy prediction for the current block. Forexample, portion 706 of the circular butter 720 may be unavailable forstoring pixels of the search area within the VPDU0 for performing theintra-block copy prediction for the current block 702. In such examples,the intra-block copy prediction for the current block 702 can beperformed by utilizing a virtual search area.

In some examples, the physical memory can include a line buffer forstoring reconstructed pixels of one or more blocks of the video data.For example, the physical memory can include a line buffer for storingreconstructed pixels of one or more blocks belonging to a neighboringcoding unit of the current CTU including the current block. For example,the physical memory can include a line buffer for storing reconstructedpixels of one or more blocks belonging to the boundary 604 a of a topneighboring CTU of the current CTU 610 and/or the boundary 604 b of aleft neighboring CTU of the current CTU 610. In some examples, thevirtual search area 606 a can include one or more references to the oneor more pixels of the boundary 604 a stored in the line buffer, and thevirtual search area 606 b can include one or more references to the oneor more pixels of the boundary 604 b stored in the line buffer. In someexamples, the one or more references in the one or more virtual searchareas to the one or more pixels stored in the physical memory caninclude repeated references to the reconstructed pixels stored in theline buffer. For example, the repeated references to the reconstructedpixels stored in the line buffer can include a first reference to atleast one reconstructed pixel stored in the line buffer and a secondreference to the at least one reconstructed pixel stored in the linebuffer.

At 906, the process 900 includes extending a search area for performingthe intra-block copy prediction for the current block to include thevirtual search area. For example, the search area for performing theintra-block copy prediction for the current block 502 in FIG. 5 can beextended to include the one or more virtual search areas 506 a-506 c. Insome examples, the intra-block copy prediction for the current block 502can be performed using one or more references to one or more pixels inthe one or more virtual search areas 506 a-506 c. For example, as shownand explained with reference to FIG. 2 and FIG. 3, a prediction blockcan be obtained within the one or more virtual search areas 506 a-506 cfor determining a block vector and generating a prediction signal forperforming the intra-block copy of the current block. In some examples,performing the intra-block copy prediction for the current block 502 caninclude reconstructing the current block 502 based on a prediction valueobtained using the intra-block copy prediction and a residual value.

In some implementations, the processes (or methods) described herein,including processes 800 and 900, can be performed by a computing deviceor an apparatus, such as the system 100 shown in FIG. 1. For example,the processes can be performed by the encoding device 104 shown in FIG.1 and FIG. 10, by another video source-side device or video transmissiondevice, by the decoding device 112 shown in FIG. 1 and FIG. 11, and/orby another client-side device, such as a player device, a display, orany other client-side device. In some examples, the computing device orapparatus may include a camera configured to capture video data (e.g., avideo sequence) including video frames. In some examples, a camera orother capture device that captures the video data is separate from thecomputing device, in which case the computing device receives or obtainsthe captured video data.

In some cases, the computing device or apparatus may include one or moreinput devices, one or more output devices, one or more processors, oneor more microprocessors, one or more microcomputers, and/or othercomponent(s) that is/are configured to carry out the steps of theprocesses described herein. In some examples, the computing device mayinclude a mobile device, a desktop computer, a server computer and/orserver system, or other type of computing device. The computing devicemay further include a network interface configured to communicate thevideo data. The network interface may be configured to communicateInternet Protocol (IP) based data or other type of data. In someexamples, the computing device or apparatus may include a display fordisplaying output video content, such as samples of pictures of a videobitstream.

The components of the computing device (e.g., the one or more inputdevices, one or more output devices, one or more processors, one or moremicroprocessors, one or more microcomputers, and/or other component) canbe implemented in circuitry. For example, the components can includeand/or can be implemented using electronic circuits or other electronichardware, which can include one or more programmable electronic circuits(e.g., microprocessors, graphics processing units (GPUs), digital signalprocessors (DSPs), central processing units (CPUs), and/or othersuitable electronic circuits), and/or can include and/or be implementedusing computer software, firmware, or any combination thereof, toperform the various operations described herein.

The processes 800 and 900 are illustrated as logical flow diagrams, theoperation of which represent a sequence of operations that can beimplemented in hardware, computer instructions, or a combinationthereof. In the context of computer instructions, the operationsrepresent computer-executable instructions stored on one or morecomputer-readable storage media that, when executed by one or moreprocessors, perform the recited operations. Generally,computer-executable instructions include routines, programs, objects,components, data structures, and the like that perform particularfunctions or implement particular data types. The order in which theoperations are described is not intended to be construed as alimitation, and any number of the described operations can be combinedin any order and/or in parallel to implement the processes.

Additionally, the processes described herein, including processes 800and 900, may be performed under the control of one or more computersystems configured with executable instructions and may be implementedas code (e.g., executable instructions, one or more computer programs,or one or more applications) executing collectively on one or moreprocessors, by hardware, or combinations thereof. As noted above, thecode may be stored on a computer-readable or machine-readable storagemedium, for example, in the form of a computer program comprising aplurality of instructions executable by one or more processors. Thecomputer-readable or machine-readable storage medium may benon-transitory.

The coding techniques discussed herein may be implemented in an examplevideo encoding and decoding system (e.g., system 100). In some examples,a system includes a source device that provides encoded video data to bedecoded at a later time by a destination device. In particular, thesource device provides the video data to destination device via acomputer-readable medium. The source device and the destination devicemay comprise any of a wide range of devices, including desktopcomputers, notebook (i.e., laptop) computers, tablet computers, set-topboxes, telephone handsets such as so-called “smart” phones, so-called“smart” pads, televisions, cameras, display devices, digital mediaplayers, video gaming consoles, video streaming device, or the like. Insome cases, the source device and the destination device may be equippedfor wireless communication.

The destination device may receive the encoded video data to be decodedvia the computer-readable medium. The computer-readable medium maycomprise any type of medium or device capable of moving the encodedvideo data from source device to destination device. In one example,computer-readable medium may comprise a communication medium to enablesource device to transmit encoded video data directly to destinationdevice in real-time. The encoded video data may be modulated accordingto a communication standard, such as a wireless communication protocol,and transmitted to destination device. The communication medium maycomprise any wireless or wired communication medium, such as a radiofrequency (RF) spectrum or one or more physical transmission lines. Thecommunication medium may form part of a packet-based network, such as alocal area network, a wide-area network, or a global network such as theInternet. The communication medium may include routers, switches, basestations, or any other equipment that may be useful to facilitatecommunication from source device to destination device.

In some examples, encoded data may be output from output interface to astorage device. Similarly, encoded data may be accessed from the storagedevice by input interface. The storage device may include any of avariety of distributed or locally accessed data storage media such as ahard drive, Blu-ray discs, DVDs, CD-ROMs, flash memory, volatile ornon-volatile memory, or any other suitable digital storage media forstoring encoded video data. In a further example, the storage device maycorrespond to a file server or another intermediate storage device thatmay store the encoded video generated by source device. Destinationdevice may access stored video data from the storage device viastreaming or download. The file server may be any type of server capableof storing encoded video data and transmitting that encoded video datato the destination device. Example file servers include a web server(e.g., for a website), an FTP server, network attached storage (NAS)devices, or a local disk drive. Destination device may access theencoded video data through any standard data connection, including anInternet connection. This may include a wireless channel (e.g., a Wi-Ficonnection), a wired connection (e.g., DSL, cable modem, etc.), or acombination of both that is suitable for accessing encoded video datastored on a file server. The transmission of encoded video data from thestorage device may be a streaming transmission, a download transmission,or a combination thereof.

The techniques of this disclosure are not necessarily limited towireless applications or settings. The techniques may be applied tovideo coding in support of any of a variety of multimedia applications,such as over-the-air television broadcasts, cable televisiontransmissions, satellite television transmissions, Internet streamingvideo transmissions, such as dynamic adaptive streaming over HTTP(DASH), digital video that is encoded onto a data storage medium,decoding of digital video stored on a data storage medium, or otherapplications. In some examples, system may be configured to supportone-way or two-way video transmission to support applications such asvideo streaming, video playback, video broadcasting, and/or videotelephony.

In one example the source device includes a video source, a videoencoder, and a output interface. The destination device may include aninput interface, a video decoder, and a display device. The videoencoder of source device may be configured to apply the techniquesdisclosed herein. In other examples, a source device and a destinationdevice may include other components or arrangements. For example, thesource device may receive video data from an external video source, suchas an external camera. Likewise, the destination device may interfacewith an external display device, rather than including an integrateddisplay device.

The example system above is merely one example. Techniques forprocessing video data in parallel may be performed by any digital videoencoding and/or decoding device. Although generally the techniques ofthis disclosure are performed by a video encoding device, the techniquesmay also be performed by a video encoder/decoder, typically referred toas a “CODEC.” Moreover, the techniques of this disclosure may also beperformed by a video preprocessor. Source device and destination deviceare merely examples of such coding devices in which source devicegenerates coded video data for transmission to destination device. Insome examples, the source and destination devices may operate in asubstantially symmetrical manner such that each of the devices includevideo encoding and decoding components. Hence, example systems maysupport one-way or two-way video transmission between video devices,e.g., for video streaming, video playback, video broadcasting, or videotelephony.

The video source may include a video capture device, such as a videocamera, a video archive containing previously captured video, and/or avideo feed interface to receive video from a video content provider. Asa further alternative, the video source may generate computergraphics-based data as the source video, or a combination of live video,archived video, and computer-generated video. In some cases, if videosource is a video camera, source device and destination device may formso-called camera phones or video phones. As mentioned above, however,the techniques described in this disclosure may be applicable to videocoding in general, and may be applied to wireless and/or wiredapplications. In each case, the captured, pre-captured, orcomputer-generated video may be encoded by the video encoder. Theencoded video information may then be output by output interface ontothe computer-readable medium.

As noted the computer-readable medium may include transient media, suchas a wireless broadcast or wired network transmission, or storage media(that is, non-transitory storage media), such as a hard disk, flashdrive, compact disc, digital video disc, Blu-ray disc, or othercomputer-readable media. In some examples, a network server (not shown)may receive encoded video data from the source device and provide theencoded video data to the destination device, e.g., via networktransmission. Similarly, a computing device of a medium productionfacility, such as a disc stamping facility, may receive encoded videodata from the source device and produce a disc containing the encodedvideo data. Therefore, the computer-readable medium may be understood toinclude one or more computer-readable media of various forms, in variousexamples.

The input interface of the destination device receives information fromthe computer-readable medium. The information of the computer-readablemedium may include syntax information defined by the video encoder,which is also used by the video decoder, that includes syntax elementsthat describe characteristics and/or processing of blocks and othercoded units, e.g., group of pictures (GOP). A display device displaysthe decoded video data to a user, and may comprise any of a variety ofdisplay devices such as a cathode ray tube (CRT), a liquid crystaldisplay (LCD), a plasma display, an organic light emitting diode (OLED)display, or another type of display device. Various embodiments of theapplication have been described.

Specific details of the encoding device 104 and the decoding device 112are shown in FIG. 10 and FIG. 1I, respectively. FIG. 10 is a blockdiagram illustrating an example encoding device 104 that may implementone or more of the techniques described in this disclosure. Encodingdevice 104 may, for example, generate the syntax structures describedherein (e.g., the syntax structures of a VPS, SPS, PPS, or other syntaxelements). Encoding device 104 may perform intra-prediction andinter-prediction coding of video blocks within video slices. Aspreviously described, intra-coding relies, at least in part, on spatialprediction to reduce or remove spatial redundancy within a given videoframe or picture. Inter-coding relies, at least in part, on temporalprediction to reduce or remove temporal redundancy within adjacent orsurrounding frames of a video sequence. Intra-mode (I mode) may refer toany of several spatial based compression modes. Inter-modes, such asuni-directional prediction (P mode) or bi-prediction (B mode), may referto any of several temporal-based compression modes.

The encoding device 104 includes a partitioning unit 35, predictionprocessing unit 41, filter unit 63, picture memory 64, summer 50,transform processing unit 52, quantization unit 54, and entropy encodingunit 56. Prediction processing unit 41 includes motion estimation unit42, motion compensation unit 44, and intra-prediction processing unit46. For video block reconstruction, encoding device 104 also includesinverse quantization unit 58, inverse transform processing unit 60, andsummer 62. Filter unit 63 is intended to represent one or more loopfilters such as a deblocking filter, an adaptive loop filter (ALF), anda sample adaptive offset (SAO) filter. Although filter unit 63 is shownin FIG. 10 as being an in loop filter, in other configurations, filterunit 63 may be implemented as a post loop filter. A post processingdevice 57 may perform additional processing on encoded video datagenerated by the encoding device 104. The techniques of this disclosuremay in some instances be implemented by the encoding device 104. Inother instances, however, one or more of the techniques of thisdisclosure may be implemented by post processing device 57.

As shown in FIG. 10, the encoding device 104 receives video data, andpartitioning unit 35 partitions the data into video blocks. Thepartitioning may also include partitioning into slices, slice segments,tiles, or other larger units, as wells as video block partitioning,e.g., according to a quadtree structure of LCUs and CUs. The encodingdevice 104 generally illustrates the components that encode video blockswithin a video slice to be encoded. The slice may be divided intomultiple video blocks (and possibly into sets of video blocks referredto as tiles). Prediction processing unit 41 may select one of aplurality of possible coding modes, such as one of a plurality ofintra-prediction coding modes or one of a plurality of inter-predictioncoding modes, for the current video block based on error results (e.g.,coding rate and the level of distortion, or the like). Predictionprocessing unit 41 may provide the resulting intra- or inter-coded blockto summer 50 to generate residual block data and to summer 62 toreconstruct the encoded block for use as a reference picture.

Intra-prediction processing unit 46 within prediction processing unit 41may perform intra-prediction coding of the current video block relativeto one or more neighboring blocks in the same frame or slice as thecurrent block to be coded to provide spatial compression. Motionestimation unit 42 and motion compensation unit 44 within predictionprocessing unit 41 perform inter-predictive coding of the current videoblock relative to one or more predictive blocks in one or more referencepictures to provide temporal compression.

Motion estimation unit 42 may be configured to determine theinter-prediction mode for a video slice according to a predeterminedpattern for a video sequence. The predetermined pattern may designatevideo slices in the sequence as P slices, B slices, or GPB slices.Motion estimation unit 42 and motion compensation unit 44 may be highlyintegrated, but are illustrated separately for conceptual purposes.Motion estimation, performed by motion estimation unit 42, is theprocess of generating motion vectors, which estimate motion for videoblocks. A motion vector, for example, may indicate the displacement of aprediction unit (PU) of a video block within a current video frame orpicture relative to a predictive block within a reference picture.

A predictive block is a block that is found to closely match the PU ofthe video block to be coded in terms of pixel difference, which may bedetermined by sum of absolute difference (SAD), sum of square difference(SSD), or other difference metrics. In some examples, the encodingdevice 104 may calculate values for sub-integer pixel positions ofreference pictures stored in picture memory 64. For example, theencoding device 104 may interpolate values of one-quarter pixelpositions, one-eighth pixel positions, or other fractional pixelpositions of the reference picture. Therefore, motion estimation unit 42may perform a motion search relative to the full pixel positions andfractional pixel positions and output a motion vector with fractionalpixel precision.

Motion estimation unit 42 calculates a motion vector for a PU of a videoblock in an inter-coded slice by comparing the position of the PU to theposition of a predictive block of a reference picture. The referencepicture may be selected from a first reference picture list (List 0) ora second reference picture list (List 1), each of which identify one ormore reference pictures stored in picture memory 64. Motion estimationunit 42 sends the calculated motion vector to entropy encoding unit 56and motion compensation unit 44.

Motion compensation, performed by motion compensation unit 44, mayinvolve fetching or generating the predictive block based on the motionvector determined by motion estimation, possibly performinginterpolations to sub-pixel precision. Upon receiving the motion vectorfor the PU of the current video block, motion compensation unit 44 maylocate the predictive block to which the motion vector points in areference picture list. The encoding device 104 forms a residual videoblock by subtracting pixel values of the predictive block from the pixelvalues of the current video block being coded, forming pixel differencevalues. The pixel difference values form residual data for the block,and may include both luma and chroma difference components. Summer 50represents the component or components that perform this subtractionoperation. Motion compensation unit 44 may also generate syntax elementsassociated with the video blocks and the video slice for use by thedecoding device 112 in decoding the video blocks of the video slice.

Intra-prediction processing unit 46 may intra-predict a current block,as an alternative to the inter-prediction performed by motion estimationunit 42 and motion compensation unit 44, as described above. Inparticular, intra-prediction processing unit 46 may determine anintra-prediction mode to use to encode a current block. In someexamples, intra-prediction processing unit 46 may encode a current blockusing various intra-prediction modes, e.g., during separate encodingpasses, and intra-prediction unit processing 46 may select anappropriate intra-prediction mode to use from the tested modes. Forexample, intra-prediction processing unit 46 may calculaterate-distortion values using a rate-distortion analysis for the varioustested intra-prediction modes, and may select the intra-prediction modehaving the best rate-distortion characteristics among the tested modes.Rate-distortion analysis generally determines an amount of distortion(or error) between an encoded block and an original, unencoded blockthat was encoded to produce the encoded block, as well as a bit rate(that is, a number of bits) used to produce the encoded block.Intra-prediction processing unit 46 may calculate ratios from thedistortions and rates for the various encoded blocks to determine whichintra-prediction mode exhibits the best rate-distortion value for theblock.

In any case, after selecting an intra-prediction mode for a block,intra-prediction processing unit 46 may provide information indicativeof the selected intra-prediction mode for the block to entropy encodingunit 56. Entropy encoding unit 56 may encode the information indicatingthe selected intra-prediction mode. The encoding device 104 may includein the transmitted bitstream configuration data definitions of encodingcontexts for various blocks as well as indications of a most probableintra-prediction mode, an intra-prediction mode index table, and amodified intra-prediction mode index table to use for each of thecontexts. The bitstream configuration data may include a plurality ofintra-prediction mode index tables and a plurality of modifiedintra-prediction mode index tables (also referred to as codeword mappingtables).

After prediction processing unit 41 generates the predictive block forthe current video block via either inter-prediction or intra-prediction,the encoding device 104 forms a residual video block by subtracting thepredictive block from the current video block. The residual video datain the residual block may be included in one or more TUs and applied totransform processing unit 52. Transform processing unit 52 transformsthe residual video data into residual transform coefficients using atransform, such as a discrete cosine transform (DCT) or a conceptuallysimilar transform. Transform processing unit 52 may convert the residualvideo data from a pixel domain to a transform domain, such as afrequency domain.

Transform processing unit 52 may send the resulting transformcoefficients to quantization unit 54. Quantization unit 54 quantizes thetransform coefficients to further reduce bit rate. The quantizationprocess may reduce the bit depth associated with some or all of thecoefficients. The degree of quantization may be modified by adjusting aquantization parameter. In some examples, quantization unit 54 may thenperform a scan of the matrix including the quantized transformcoefficients. Alternatively, entropy encoding unit 56 may perform thescan.

Following quantization, entropy encoding unit 56 entropy encodes thequantized transform coefficients. For example, entropy encoding unit 56may perform context adaptive variable length coding (CAVLC), contextadaptive binary arithmetic coding (CABAC), syntax-based context-adaptivebinary arithmetic coding (SBAC), probability interval partitioningentropy (PIPE) coding or another entropy encoding technique. Followingthe entropy encoding by entropy encoding unit 56, the encoded bitstreammay be transmitted to the decoding device 112, or archived for latertransmission or retrieval by the decoding device 112. Entropy encodingunit 56 may also entropy encode the motion vectors and the other syntaxelements for the current video slice being coded.

Inverse quantization unit 58 and inverse transform processing unit 60apply inverse quantization and inverse transformation, respectively, toreconstruct the residual block in the pixel domain for later use as areference block of a reference picture. Motion compensation unit 44 maycalculate a reference block by adding the residual block to a predictiveblock of one of the reference pictures within a reference picture list.Motion compensation unit 44 may also apply one or more interpolationfilters to the reconstructed residual block to calculate sub-integerpixel values for use in motion estimation. Summer 62 adds thereconstructed residual block to the motion compensated prediction blockproduced by motion compensation unit 44 to produce a reference block forstorage in picture memory 64. The reference block may be used by motionestimation unit 42 and motion compensation unit 44 as a reference blockto inter-predict a block in a subsequent video frame or picture.

In this manner, the encoding device 104 of FIG. 10 represents an exampleof a video encoder configured to perform any of the techniques describedherein, including the processes described above with respect to FIG. 8and/or FIG. 9. In some cases, some of the techniques of this disclosuremay also be implemented by post processing device 57.

FIG. 11 is a block diagram illustrating an example decoding device 112.The decoding device 112 includes an entropy decoding unit 80, predictionprocessing unit 81, inverse quantization unit 86, inverse transformprocessing unit 88, summer 90, filter unit 91, and picture memory 92.Prediction processing unit 81 includes motion compensation unit 82 andintra prediction processing unit 84. The decoding device 112 may, insome examples, perform a decoding pass generally reciprocal to theencoding pass described with respect to the encoding device 104 fromFIG. 11.

During the decoding process, the decoding device 112 receives an encodedvideo bitstream that represents video blocks of an encoded video sliceand associated syntax elements sent by the encoding device 104. In someembodiments, the decoding device 112 may receive the encoded videobitstream from the encoding device 104. In some embodiments, thedecoding device 112 may receive the encoded video bitstream from anetwork entity 79, such as a server, a media-aware network element(MANE), a video editor/splicer, or other such device configured toimplement one or more of the techniques described above. Network entity79 may or may not include the encoding device 104. Some of thetechniques described in this disclosure may be implemented by networkentity 79 prior to network entity 79 transmitting the encoded videobitstream to the decoding device 112. In some video decoding systems,network entity 79 and the decoding device 112 may be parts of separatedevices, while in other instances, the functionality described withrespect to network entity 79 may be performed by the same device thatcomprises the decoding device 112.

The entropy decoding unit 80 of the decoding device 112 entropy decodesthe bitstream to generate quantized coefficients, motion vectors, andother syntax elements. Entropy decoding unit 80 forwards the motionvectors and other syntax elements to prediction processing unit 81. Thedecoding device 112 may receive the syntax elements at the video slicelevel and/or the video block level. Entropy decoding unit 80 may processand parse both fixed-length syntax elements and variable-length syntaxelements in or more parameter sets, such as a VPS, SPS, and PPS.

When the video slice is coded as an intra-coded (1) slice, intraprediction processing unit 84 of prediction processing unit 81 maygenerate prediction data for a video block of the current video slicebased on a signaled intra-prediction mode and data from previouslydecoded blocks of the current frame or picture. When the video frame iscoded as an inter-coded (i.e., B, P or GPB) slice, motion compensationunit 82 of prediction processing unit 81 produces predictive blocks fora video block of the current video slice based on the motion vectors andother syntax elements received from entropy decoding unit 80. Thepredictive blocks may be produced from one of the reference pictureswithin a reference picture list. The decoding device 112 may constructthe reference frame lists, List 0 and List 1, using default constructiontechniques based on reference pictures stored in picture memory 92.

Motion compensation unit 82 determines prediction information for avideo block of the current video slice by parsing the motion vectors andother syntax elements, and uses the prediction information to producethe predictive blocks for the current video block being decoded. Forexample, motion compensation unit 82 may use one or more syntax elementsin a parameter set to determine a prediction mode (e.g., intra- orinter-prediction) used to code the video blocks of the video slice, aninter-prediction slice type (e.g., B slice, P slice, or GPB slice),construction information for one or more reference picture lists for theslice, motion vectors for each inter-encoded video block of the slice,inter-prediction status for each inter-coded video block of the slice,and other information to decode the video blocks in the current videoslice.

Motion compensation unit 82 may also perform interpolation based oninterpolation filters. Motion compensation unit 82 may use interpolationfilters as used by the encoding device 104 during encoding of the videoblocks to calculate interpolated values for sub-integer pixels ofreference blocks. In this case, motion compensation unit 82 maydetermine the interpolation filters used by the encoding device 104 fromthe received syntax elements, and may use the interpolation filters toproduce predictive blocks.

Inverse quantization unit 86 inverse quantizes, or de-quantizes, thequantized transform coefficients provided in the bitstream and decodedby entropy decoding unit 80. The inverse quantization process mayinclude use of a quantization parameter calculated by the encodingdevice 104 for each video block in the video slice to determine a degreeof quantization and, likewise, a degree of inverse quantization thatshould be applied. Inverse transform processing unit 88 applies aninverse transform (e.g., an inverse DCT or other suitable inversetransform), an inverse integer transform, or a conceptually similarinverse transform process, to the transform coefficients in order toproduce residual blocks in the pixel domain.

After motion compensation unit 82 generates the predictive block for thecurrent video block based on the motion vectors and other syntaxelements, the decoding device 112 forms a decoded video block by summingthe residual blocks from inverse transform processing unit 88 with thecorresponding predictive blocks generated by motion compensation unit82. Summer 90 represents the component or components that perform thissummation operation. If desired, loop filters (either in the coding loopor after the coding loop) may also be used to smooth pixel transitions,or to otherwise improve the video quality. Filter unit 91 is intended torepresent one or more loop filters such as a deblocking filter, anadaptive loop filter (ALF), and a sample adaptive offset (SAO) filter.Although filter unit 91 is shown in FIG. 11 as being an in loop filter,in other configurations, filter unit 91 may be implemented as a postloop filter. The decoded video blocks in a given frame or picture arethen stored in picture memory 92, which stores reference pictures usedfor subsequent motion compensation. Picture memory 92 also storesdecoded video for later presentation on a display device, such as videodestination device 122 shown in FIG. 1.

In this manner, the decoding device 112 of FIG. 11 represents an exampleof a video decoder configured to perform any of the techniques describedherein, including the processes described above with respect to FIG. 8and/or FIG. 9.

As used herein, the term “computer-readable medium” includes, but is notlimited to, portable or non-portable storage devices, optical storagedevices, and various other mediums capable of storing, containing, orcarrying instruction(s) and/or data. A computer-readable medium mayinclude a non-transitory medium in which data can be stored and thatdoes not include carrier waves and/or transitory electronic signalspropagating wirelessly or over wired connections. Examples of anon-transitory medium may include, but are not limited to, a magneticdisk or tape, optical storage media such as compact disk (CD) or digitalversatile disk (DVD), flash memory, memory or memory devices. Acomputer-readable medium may have stored thereon code and/ormachine-executable instructions that may represent a procedure, afunction, a subprogram, a program, a routine, a subroutine, a module, asoftware package, a class, or any combination of instructions, datastructures, or program statements. A code segment may be coupled toanother code segment or a hardware circuit by passing and/or receivinginformation, data, arguments, parameters, or memory contents.Information, arguments, parameters, data, etc. may be passed, forwarded,or transmitted via any suitable means including memory sharing, messagepassing, token passing, network transmission, or the like.

In some embodiments the computer-readable storage devices, mediums, andmemories can include a cable or wireless signal containing a bit streamand the like. However, when mentioned, non-transitory computer-readablestorage media expressly exclude media such as energy, carrier signals,electromagnetic waves, and signals per se.

Specific details are provided in the description above to provide athorough understanding of the embodiments and examples provided herein.However, it will be understood by one of ordinary skill in the art thatthe embodiments may be practiced without these specific details. Forclarity of explanation, in some instances the present technology may bepresented as including individual functional blocks including functionalblocks comprising devices, device components, steps or routines in amethod embodied in software, or combinations of hardware and software.Additional components may be used other than those shown in the figuresand/or described herein. For example, circuits, systems, networks,processes, and other components may be shown as components in blockdiagram form in order not to obscure the embodiments in unnecessarydetail. In other instances, well-known circuits, processes, algorithms,structures, and techniques may be shown without unnecessary detail inorder to avoid obscuring the embodiments.

Individual embodiments may be described above as a process or methodwhich is depicted as a flowchart, a flow diagram, a data flow diagram, astructure diagram, or a block diagram. Although a flowchart may describethe operations as a sequential process, many of the operations can beperformed in parallel or concurrently. In addition, the order of theoperations may be re-arranged. A process is terminated when itsoperations are completed, but could have additional steps not includedin a figure. A process may correspond to a method, a function, aprocedure, a subroutine, a subprogram, etc. When a process correspondsto a function, its termination can correspond to a return of thefunction to the calling function or the main function.

Processes and methods according to the above-described examples can beimplemented using computer-executable instructions that are stored orotherwise available from computer-readable media. Such instructions caninclude, for example, instructions and data which cause or otherwiseconfigure a general purpose computer, special purpose computer, or aprocessing device to perform a certain function or group of functions.Portions of computer resources used can be accessible over a network.The computer executable instructions may be, for example, binaries,intermediate format instructions such as assembly language, firmware,source code, etc. Examples of computer-readable media that may be usedto store instructions, information used, and/or information createdduring methods according to described examples include magnetic oroptical disks, flash memory, USB devices provided with non-volatilememory, networked storage devices, and so on.

Devices implementing processes and methods according to thesedisclosures can include hardware, software, firmware, middleware,microcode, hardware description languages, or any combination thereof,and can take any of a variety of form factors. When implemented insoftware, firmware, middleware, or microcode, the program code or codesegments to perform the necessary tasks (e.g., a computer-programproduct) may be stored in a computer-readable or machine-readablemedium. A processor(s) may perform the necessary tasks. Typical examplesof form factors include laptops, smart phones, mobile phones, tabletdevices or other small form factor personal computers, personal digitalassistants, rackmount devices, standalone devices, and so on.Functionality described herein also can be embodied in peripherals oradd-in cards. Such functionality can also be implemented on a circuitboard among different chips or different processes executing in a singledevice, by way of further example.

The instructions, media for conveying such instructions, computingresources for executing them, and other structures for supporting suchcomputing resources are example means for providing the functionsdescribed in the disclosure.

In the foregoing description, aspects of the application are describedwith reference to specific embodiments thereof, but those skilled in theart will recognize that the application is not limited thereto. Thus,while illustrative embodiments of the application have been described indetail herein, it is to be understood that the inventive concepts may beotherwise variously embodied and employed, and that the appended claimsare intended to be construed to include such variations, except aslimited by the prior art. Various features and aspects of theabove-described application may be used individually or jointly.Further, embodiments can be utilized in any number of environments andapplications beyond those described herein without departing from thebroader spirit and scope of the specification. The specification anddrawings are, accordingly, to be regarded as illustrative rather thanrestrictive. For the purposes of illustration, methods were described ina particular order. It should be appreciated that in alternateembodiments, the methods may be performed in a different order than thatdescribed.

One of ordinary skill will appreciate that the less than (“<”) andgreater than (“>”) symbols or terminology used herein can be replacedwith less than or equal to (“≤”) and greater than or equal to (“≥”)symbols, respectively, without departing from the scope of thisdescription.

Where components are described as being “configured to” perform certainoperations, such configuration can be accomplished, for example, bydesigning electronic circuits or other hardware to perform theoperation, by programming programmable electronic circuits (e.g.,microprocessors, or other suitable electronic circuits) to perform theoperation, or any combination thereof.

The phrase “coupled to” refers to any component that is physicallyconnected to another component either directly or indirectly, and/or anycomponent that is in communication with another component (e.g.,connected to the other component over a wired or wireless connection,and/or other suitable communication interface) either directly orindirectly.

Claim language or other language reciting “at least one of” a set and/or“one or more” of a set indicates that one member of the set or multiplemembers of the set (in any combination) satisfy the claim. For example,claim language reciting “at least one of A and B” means A, B, or A andB. In another example, claim language reciting “at least one of A, B,and C” means A, B, C, or A and B, or A and C, or B and C, or A and B andC. The language “at least one of” a set and/or “one or more” of a setdoes not limit the set to the items listed in the set. For example,claim language reciting “at least one of A and B” can mean A, B, or Aand B, and can additionally include items not listed in the set of A andB.

The various illustrative logical blocks, modules, circuits, andalgorithm steps described in connection with the embodiments disclosedherein may be implemented as electronic hardware, computer software,firmware, or combinations thereof. To clearly illustrate thisinterchangeability of hardware and software, various illustrativecomponents, blocks, modules, circuits, and steps have been describedabove generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present application.

The techniques described herein may also be implemented in electronichardware, computer software, firmware, or any combination thereof. Suchtechniques may be implemented in any of a variety of devices such asgeneral purposes computers, wireless communication device handsets, orintegrated circuit devices having multiple uses including application inwireless communication device handsets and other devices. Any featuresdescribed as modules or components may be implemented together in anintegrated logic device or separately as discrete but interoperablelogic devices. If implemented in software, the techniques may berealized at least in part by a computer-readable data storage mediumcomprising program code including instructions that, when executed,performs one or more of the methods described above. Thecomputer-readable data storage medium may form part of a computerprogram product, which may include packaging materials. Thecomputer-readable medium may comprise memory or data storage media, suchas random access memory (RAM) such as synchronous dynamic random accessmemory (SDRAM), read-only memory (ROM), non-volatile random accessmemory (NVRAM), electrically erasable programmable read-only memory(EEPROM), FLASH memory, magnetic or optical data storage media, and thelike. The techniques additionally, or alternatively, may be realized atleast in part by a computer-readable communication medium that carriesor communicates program code in the form of instructions or datastructures and that can be accessed, read, and/or executed by acomputer, such as propagated signals or waves.

The program code may be executed by a processor, which may include oneor more processors, such as one or more digital signal processors(DSPs), general purpose microprocessors, an application specificintegrated circuits (ASICs), field programmable logic arrays (FPGAs), orother equivalent integrated or discrete logic circuitry. Such aprocessor may be configured to perform any of the techniques describedin this disclosure. A general purpose processor may be a microprocessor;but in the alternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration. Accordingly, the term “processor,” as used herein mayrefer to any of the foregoing structure, any combination of theforegoing structure, or any other structure or apparatus suitable forimplementation of the techniques described herein. In addition, in someaspects, the functionality described herein may be provided withindedicated software modules or hardware modules configured for encodingand decoding, or incorporated in a combined video encoder-decoder(CODEC).

Illustrative examples of the disclosure include:

Example 1

A method of decoding video data. The method includes: obtaining anencoded video bitstream including video data; generating a virtualsearch area for performing intra-block copy prediction for a currentblock of the video data, the virtual search area including one or morereferences to one or more pixels stored in a physical memory; andextending a search area for performing the intra-block copy predictionfor the current block to include the virtual search area.

Example 2

A method according to Example 1, wherein the physical memory comprises acircular buffer for storing reconstructed pixels of a coding unitcomprising one or more blocks of the video data.

Example 3

A method according to any of Examples 1 or 2, wherein the one or morepixels stored in the physical memory comprise reconstructed pixelsbelonging to a boundary of the coding unit.

Example 4

A method according to any of Examples 1 to 3, wherein the one or morereferences to the one or more pixels stored in the physical memorycomprise repeated references to the reconstructed pixels belonging tothe boundary.

Example 5

A method according to any of Examples 1 to 4, wherein the repeatedreferences to the reconstructed pixels belonging to the boundarycomprise a first reference to at least one reconstructed pixel belongingto the boundary and a second reference to the at least one reconstructedpixel belonging to the boundary.

Example 6

A method according to any of Examples 1 to 5, wherein the current blockbelongs to the coding unit.

Example 7

A method according to any of Examples 1 to 6, wherein the coding unitincludes two or more virtual pipeline data units (VPDUs), at least oneVPDU of the two or more VPDUs comprising the current block, and whereinat least a portion of the circular buffer is configured to storereconstructed pixels of the at least one VPDU while intra-block copyprediction is being performed on the one or more blocks of the at leastone VPDU.

Example 8

A method according to any of Examples 1 to 7, wherein at least theportion of the circular buffer is unavailable for storing pixels of thesearch area for performing the intra-block copy prediction for thecurrent block.

Example 9

A method according to any of Examples 1 to 8, wherein the physicalmemory comprises a line buffer for storing reconstructed pixels of oneor more blocks of the video data.

Example 10

A method according to any of Examples 1 to 9, wherein the one or moreblocks belong to a neighboring coding unit of a current coding unitcomprising the current block.

Example 11

A method according to any of Examples 1 to 10, wherein the one or morereferences to the one or more pixels stored in the physical memorycomprise repeated references to the reconstructed pixels stored in theline buffer.

Example 12

A method according to any of Examples 1 to 11, wherein the repeatedreferences to the reconstructed pixels stored in the line buffercomprise a first reference to at least one reconstructed pixel stored inthe line buffer and a second reference to the at least one reconstructedpixel stored in the line buffer.

Example 13

A method according to any of Examples 1 to 12, further comprising:performing the intra-block copy prediction for the current block usingone or more references to one or more pixels in the virtual search area.

Example 14

A method according to any of Examples 1 to 13, further comprising:reconstructing the current block based on a prediction value obtainedusing the intra-block copy prediction and a residual value.

Example 15

An apparatus for decoding video data, the apparatus comprising: amemory; and a processor implemented in circuitry and configured to:obtain an encoded video bitstream including video data; generate avirtual search area for performing intra-block copy prediction for acurrent block of the video data, the virtual search area including oneor more references to one or more pixels stored in a physical memory;and extend a search area for performing the intra-block copy predictionfor the current block to include the virtual search area.

Example 16

An apparatus according to Example 15, wherein the physical memorycomprises a circular buffer for storing reconstructed pixels of a codingunit comprising one or more blocks of the video data.

Example 17

An apparatus according to any of Examples 15 to 16, wherein the one ormore pixels stored in the physical memory comprise reconstructed pixelsbelonging to a boundary of the coding unit.

Example 18

An apparatus according to any of Examples 15 to 17, wherein the one ormore references to the one or more pixels stored in the physical memorycomprise repeated references to the reconstructed pixels belonging tothe boundary.

Example 19

An apparatus according to any of Examples 15 to 18, wherein the repeatedreferences to the reconstructed pixels belonging to the boundarycomprise a first reference to at least one reconstructed pixel belongingto the boundary and a second reference to the at least one reconstructedpixel belonging to the boundary.

Example 20

An apparatus according to any of Examples 15 to 19, wherein the currentblock belongs to the coding unit.

Example 21

An apparatus according to any of Examples 15 to 20, wherein the codingunit includes two or more virtual pipeline data units (VPDUs), at leastone VPDU of the two or more VPDUs comprising the current block, andwherein at least a portion of the circular buffer is configured to storereconstructed pixels of the at least one VPDU while intra-block copyprediction is being performed on the one or more blocks of the at leastone VPDU.

Example 22

An apparatus according to any of Examples 15 to 21, wherein at least theportion of the circular buffer is unavailable for storing pixels of thesearch area for performing the intra-block copy prediction for thecurrent block.

Example 23

An apparatus according to any of Examples 15 to 22, wherein the physicalmemory comprises a line buffer for storing reconstructed pixels of oneor more blocks of the video data.

Example 24

An apparatus according to any of Examples 15 to 23, wherein the one ormore blocks belong to a neighboring coding unit of a current coding unitcomprising the current block.

Example 25

An apparatus according to any of Examples 15 to 24, wherein the one ormore references to the one or more pixels stored in the physical memorycomprise repeated references to the reconstructed pixels stored in theline buffer.

Example 26

An apparatus according to any of Examples 15 to 25, wherein theprocessor is further configured to: perform the intra-block copyprediction for the current block using one or more references to one ormore pixels in the virtual search area.

Example 27

An apparatus according to any of Examples 15 to 26, wherein theapparatus comprises a mobile device with a camera for capturing the oneor more pictures.

Example 28

An apparatus according to any of Examples 15 to 27, further comprising adisplay for displaying the one or more pictures.

Example 29

A non-transitory computer-readable medium having stored thereoninstructions that when executed by a processor perform the methods ofany of examples 1 to 14. For example, the non-transitorycomputer-readable medium can have stored thereon instructions that, whenexecuted by one or more processors, cause the one or more processors to:obtain an encoded video bitstream including video data; generate avirtual search area for performing intra-block copy prediction for acurrent block of the video data, the virtual search area including oneor more references to one or more pixels stored in a physical memory;and extend a search area for performing the intra-block copy predictionfor the current block to include the virtual search area.

Example 30

An apparatus for decoding video data according to any of the examples 1to 14. The apparatus includes: means for obtaining an encoded videobitstream including video data; means for generating a virtual searcharea for performing intra-block copy prediction for a current block ofthe video data, the virtual search area including one or more referencesto one or more pixels stored in a physical memory; and means forextending a search area for performing the intra-block copy predictionfor the current block to include the virtual search area.

Example 31

A method for encoding video data. The method includes: obtaining acurrent block of a picture of video data; generating a virtual searcharea for performing intra-block copy prediction for the current block,the virtual search area including one or more references to one or morepixels stored in a physical memory; extending a search area forperforming the intra-block copy prediction for the current block toinclude the virtual search area; and generating an encoded videobitstream including at least a portion of the current block.

Example 32

A method according to Example 31, wherein the physical memory comprisesa circular buffer for storing reconstructed pixels of a coding unitcomprising one or more blocks of the video data.

Example 33

A method according to any of Examples 31 or 32, wherein the one or morepixels stored in the physical memory comprise reconstructed pixelsbelonging to a boundary of the coding unit.

Example 34

A method according to any of Examples 31 to 33, wherein the one or morereferences to the one or more pixels stored in the physical memorycomprise repeated references to the reconstructed pixels belonging tothe boundary.

Example 35

A method according to any of Examples 31 to 34, wherein the repeatedreferences to the reconstructed pixels belonging to the boundarycomprise a first reference to at least one reconstructed pixel belongingto the boundary and a second reference to the at least one reconstructedpixel belonging to the boundary.

Example 36

A method according to any of Examples 31 to 35, wherein the currentblock belongs to the coding unit.

Example 37

A method according to any of Examples 31 to 36, wherein the coding unitincludes two or more virtual pipeline data units (VPDUs), at least oneVPDU of the two or more VPDUs comprising the current block, and whereinat least a portion of the circular buffer is configured to storereconstructed pixels of the at least one VPDU while intra-block copyprediction is being performed on the one or more blocks of the at leastone VPDU.

Example 38

A method according to any of Examples 31 to 37, wherein at least theportion of the circular buffer is unavailable for storing pixels of thesearch area for performing the intra-block copy prediction for thecurrent block.

Example 39

A method according to any of Examples 31 to 38, wherein the physicalmemory comprises a line buffer for storing reconstructed pixels of oneor more blocks of the video data.

Example 40

A method according to any of Examples 31 to 39, wherein the one or moreblocks belong to a neighboring coding unit of a current coding unitcomprising the current block.

Example 41

A method according to any of Examples 31 to 40, wherein the one or morereferences to the one or more pixels stored in the physical memorycomprise repeated references to the reconstructed pixels stored in theline buffer.

Example 42

A method according to any of Examples 31 to 41, wherein the repeatedreferences to the reconstructed pixels stored in the line buffercomprise a first reference to at least one reconstructed pixel stored inthe line buffer and a second reference to the at least one reconstructedpixel stored in the line buffer.

Example 43

A method according to any of Examples 31 to 42, further comprising:performing the intra-block copy prediction for the current block usingone or more references to one or more pixels in the virtual search area.

Example 44

A method according to any of Examples 31 to 43, further comprising:reconstructing the current block based on a prediction value obtainedusing the intra-block copy prediction and a residual value.

Example 45

An apparatus for encoding video data according to any of the methods 31to 44. The apparatus comprises a memory and a processor implemented incircuitry and configured to: obtain a current block of a picture ofvideo data; generate a virtual search area for performing intra-blockcopy prediction for the current block, the virtual search area includingone or more references to one or more pixels stored in a physicalmemory; extend a search area for performing the intra-block copyprediction for the current block to include the virtual search area; andgenerate an encoded video bitstream including at least a portion of thecurrent block.

Example 46

A non-transitory computer-readable medium having stored thereoninstructions that, when executed by one or more processors, cause theone or more processors to perform the methods of any of examples 31 to44. For example, the non-transitory computer-readable medium can havestored thereon instructions that, when executed by one or moreprocessors, cause the one or more processors to: obtain a current blockof a picture of video data; generate a virtual search area forperforming intra-block copy prediction for the current block, thevirtual search area including one or more references to one or morepixels stored in a physical memory; extend a search area for performingthe intra-block copy prediction for the current block to include thevirtual search area: and generate an encoded video bitstream includingat least a portion of the current block.

Example 47

An apparatus for decoding video data according to any of the examples 31to 44. The apparatus includes: means for obtaining a current block of apicture of video data; means for generating a virtual search area forperforming intra-block copy prediction for the current block, thevirtual search area including one or more references to one or morepixels stored in a physical memory; means for extending a search areafor performing the intra-block copy prediction for the current block toinclude the virtual search area; and means for generating an encodedvideo bitstream including at least a portion of the current block.

Example 48

A method of processing video data. The method includes: obtaining videodata; determining intra-block copy prediction is enabled for performingintra-picture prediction on at least one block of the video data; andgenerating an extended search reference area for the intra-block copyprediction for the at least one block, the extended search referencearea being generated by adding padding pixels at a search range boundaryassociated with the intra-block copy prediction.

Example 49

A method according to Example 48, wherein the padding pixels includerepeating boundary pixels from a boundary of a current reference area.

Example 50

A method according to any of Examples 48 to 49, wherein the paddingpixels include repeating boundary pixels of one or more neighboringblocks.

Example 51

A method according to any of Examples 48 to 50, wherein the boundarypixels of the one or more neighboring blocks are obtained from a linebuffer.

Example 52

A method according to any of Examples 48 to 51, wherein the extendedsearch reference area is stored using a circular buffer.

Example 53

A method according to any of Examples 33 to 52, wherein a storage regionof the circular buffer including reconstructed pixels of a neighboringcoding unit is updated using reconstructed pixels of a current codingunit, the current coding unit including the at least one block.

Example 54

A method according to any of Examples 48 to 53, wherein the storageregion being updated is not a search reference area.

Example 55

A method according to any of Examples 48 to 54, wherein the storageregion is replaced by one or more padding pixels from the extendedsearch reference area.

Example 56

A method according to any of Examples 48 to 55, further comprisingsignaling an indication of the extended search reference area in anencoded video bitstream.

Example 57

A method according to any of Examples 48 to 56, further comprising:performing the intra-block copy prediction for the at least one blockusing the extended search reference area.

Example 58

An apparatus comprising a memory configured to store video data and aprocessor configured to process the video data according to any of theExamples 48 to 57.

Example 59

An apparatus according to Example 58, wherein the apparatus includes adecoder.

Example 60

An apparatus according to Example 58, wherein the apparatus includes anencoder.

Example 61

An apparatus according to any of Examples 58 to 60, wherein theapparatus is a mobile device.

Example 62

An apparatus according to any of Examples 58 to 61, wherein theapparatus includes a display configured to display the video data.

Example 63

An apparatus according to any of Examples 58 to 62, wherein theapparatus includes a camera configured to capture one or more pictures.

Example 64

A computer readable medium having stored thereon instructions that whenexecuted by a processor perform the methods of any of claims 48 to 57.

What is claimed is:
 1. A method of decoding video data, the methodcomprising: obtaining an encoded video bitstream including video data;generating a virtual search area for performing intra-block copyprediction for a current block of the video data, the virtual searcharea including one or more references to one or more pixels stored in aphysical memory; and extending a search area for performing theintra-block copy prediction for the current block to include the virtualsearch area.
 2. The method of claim 1, wherein the physical memorycomprises a circular buffer for storing reconstructed pixels of a codingunit comprising one or more blocks of the video data.
 3. The method ofclaim 2, wherein the one or more pixels stored in the physical memorycomprise reconstructed pixels belonging to a boundary of the codingunit.
 4. The method of claim 3, wherein the one or more references tothe one or more pixels stored in the physical memory comprise repeatedreferences to the reconstructed pixels belonging to the boundary.
 5. Themethod of claim 4, wherein the repeated references to the reconstructedpixels belonging to the boundary comprise a first reference to at leastone reconstructed pixel belonging to the boundary and a second referenceto the at least one reconstructed pixel belonging to the boundary. 6.The method of claim 2, wherein the current block belongs to the codingunit.
 7. The method of claim 2, wherein the coding unit includes two ormore virtual pipeline data units (VPDUs), at least one VPDU of the twoor more VPDUs comprising the current block, and wherein at least aportion of the circular buffer is configured to store reconstructedpixels of the at least one VPDU while intra-block copy prediction isbeing performed on the one or more blocks of the at least one VPDU. 8.The method of claim 7, wherein at least the portion of the circularbuffer is unavailable for storing pixels of the search area forperforming the intra-block copy prediction for the current block.
 9. Themethod of claim 1, wherein the physical memory comprises a line bufferfor storing reconstructed pixels of one or more blocks of the videodata.
 10. The method of claim 9, wherein the one or more blocks belongto a neighboring coding unit of a current coding unit comprising thecurrent block.
 11. The method of claim 9, wherein the one or morereferences to the one or more pixels stored in the physical memorycomprise repeated references to the reconstructed pixels stored in theline buffer.
 12. The method of claim 11, wherein the repeated referencesto the reconstructed pixels stored in the line buffer comprise a firstreference to at least one reconstructed pixel stored in the line bufferand a second reference to the at least one reconstructed pixel stored inthe line buffer.
 13. The method of claim 1, further comprising:performing the intra-block copy prediction for the current block usingone or more references to one or more pixels in the virtual search area.14. The method of claim 1, further comprising: reconstructing thecurrent block based on a prediction value obtained using the intra-blockcopy prediction and a residual value.
 15. An apparatus for decodingvideo data, the apparatus comprising: a memory; and a processorimplemented in circuitry and configured to: obtain an encoded videobitstream including video data; generate a virtual search area forperforming intra-block copy prediction for a current block of the videodata, the virtual search area including one or more references to one ormore pixels stored in a physical memory; and extend a search area forperforming the intra-block copy prediction for the current block toinclude the virtual search area.
 16. The apparatus of claim 15, whereinthe physical memory comprises a circular buffer for storingreconstructed pixels of a coding unit comprising one or more blocks ofthe video data.
 17. The apparatus of claim 16, wherein the one or morepixels stored in the physical memory comprise reconstructed pixelsbelonging to a boundary of the coding unit.
 18. The apparatus of claim17, wherein the one or more references to the one or more pixels storedin the physical memory comprise repeated references to the reconstructedpixels belonging to the boundary.
 19. The apparatus of claim 18, whereinthe repeated references to the reconstructed pixels belonging to theboundary comprise a first reference to at least one reconstructed pixelbelonging to the boundary and a second reference to the at least onereconstructed pixel belonging to the boundary.
 20. The apparatus ofclaim 16, wherein the current block belongs to the coding unit.
 21. Theapparatus of claim 16, wherein the coding unit includes two or morevirtual pipeline data units (VPDUs), at least one VPDU of the two ormore VPDUs comprising the current block, and wherein at least a portionof the circular buffer is configured to store reconstructed pixels ofthe at least one VPDU while intra-block copy prediction is beingperformed on the one or more blocks of the at least one VPDU.
 22. Theapparatus of claim 21, wherein at least the portion of the circularbuffer is unavailable for storing pixels of the search area forperforming the intra-block copy prediction for the current block. 23.The apparatus of claim 15, wherein the physical memory comprises a linebuffer for storing reconstructed pixels of one or more blocks of thevideo data.
 24. The apparatus of claim 23, wherein the one or moreblocks belong to a neighboring coding unit of a current coding unitcomprising the current block.
 25. The apparatus of claim 23, wherein theone or more references to the one or more pixels stored in the physicalmemory comprise repeated references to the reconstructed pixels storedin the line buffer.
 26. The apparatus of claim 15, wherein the processoris further configured to: perform the intra-block copy prediction forthe current block using one or more references to one or more pixels inthe virtual search area.
 27. The apparatus of claim 15, wherein theapparatus comprises a mobile device with a camera for capturing one ormore pictures.
 28. The apparatus of claim 15, further comprising adisplay for displaying one or more pictures.
 29. A non-transitorycomputer-readable medium having stored thereon instructions that, whenexecuted by one or more processors, cause the one or more processors to:obtain an encoded video bitstream including video data; generate avirtual search area for performing intra-block copy prediction for acurrent block of the video data, the virtual search area including oneor more references to one or more pixels stored in a physical memory;and extend a search area for performing the intra-block copy predictionfor the current block to include the virtual search area.
 30. Anapparatus for encoding video data, the apparatus comprising: a memory;and a processor implemented in circuitry and configured to: obtain acurrent block of a picture of video data; generate a virtual search areafor performing intra-block copy prediction for the current block, thevirtual search area including one or more references to one or morepixels stored in a physical memory; extend a search area for performingthe intra-block copy prediction for the current block to include thevirtual search area; and generate an encoded video bitstream includingat least a portion of the current block.